Spire Height Research Articles

Shell morphology and reproductive anatomy of Levantina mardinensis (Gastropoda, Helicidae) from a new locality of Mardin, Türkiye

ABSTRACT The genus Levantina Kobelt, 1871, comprises 25 taxa inhabiting rocky environments across the Middle East. This study focuses on documenting a new location of L. mardinensis Kobelt, 1900, and provides a detailed analysis of its shell morphology and reproductive anatomy, contributing to the knowledge and conservation of this land snail from Mardin, southeastern Türkiye. The distribution of L. mardinensis is widespread in Mardin Province and extends into northern Syria and Iraq. The study provides measurements for previously unreported shell characteristics of specimens from Eskikale (Mardin), including aperture height, aperture width, spire height, and body whorl height, with high-resolution images for visual reference.

Morphometric variation and species density of Nerita (Neritidae: Gastropoda) in the coastal waters of Ambon Island, Indonesia

Nerita is one of the species with high diversity in the coastal waters of Ambon Island. With this high diversity, the way to assess the length of various Nerita species is through a morphometric study. Meanwhile, density studies are useful for knowing the number of each of these diverse Nerita species. The purpose of this study was to identify the Nerita species to calculate the density and morphometrics. This research was conducted in an intertidal area in two locations, namely Seri and Tawiri villages. The morphometric characteristics of Nerita consist of shell length, shell width, aperture length, spire height, columella length, aperture length, and lip thickness. The density calculation refers to the density formula. The results showed that there were 9 species of Nerita, namely N. polita, N. chamaeleon, N. patula, N. exuvia, N. maxima, N. squamulata, N. albicilla, and N. planospira. N. polita has the highest density value (41.33 ind/m2) while N. patula (0.04 ind/m2) has the lowest density value. Morphometric analysis shows that there are variations in shell size among these species. Shell morphometric variations can be used as a reference for studying the phenetic diversity of Neritaidae in Ambon Island waters

Theoretical morphological analysis of differential morphospace occupation patterns for terrestrial and aquatic gastropods.

Despite the morphological diversity of organisms, they only occupy a fraction of the theoretically possible spectrum (i.e., morphospace) and have been studied on several taxa. Such morphospace occupation patterns are formed through evolutionary processes under multiple constraints. In this study, we discovered a differential morphospace occupation pattern between terrestrial and aquatic gastropods, and subsequently attempted to quantitatively understand these differences through morphospace analysis. These differential occupation patterns between terrestrial and aquatic species were observed in the morphospace of spire height and aperture inclination, including a bimodal distribution of shell height in terrestrial species alongside an absence of high-spired shells with high aperture inclination. Although terrestrial species were distributed along optimal lines of shell instability and shell hindrance to locomotion, aquatic species were distributed not only along this line but also within a suboptimal region of the low spire with low inclination. Based on numerical simulation and biometric analysis, here we propose the hypothesis that this difference was caused by the aquatic species being able to adopt a posture with the growth direction perpendicular to the substrate due to reduced functional demands. Our results provided an ultimate explanation for the differential occupation patterns between habitats alongside an overview of the morphospace.

Sexual dimorphism in shell size of the land snail Leptopoma perlucidum (Caenogastropoda: Cyclophoridae).

Sexual dimorphism in the shell size and shape of land snails has been less explored compared to that of other marine and freshwater snail taxa. This study examined the differences in shell size and shape across both sexes of Leptopoma perlucidum land snails. We collected 84 land snails of both sexes from two isolated populations on two islands off Borneo. A total of five shell size variables were measured: (1) shell height, (2) shell width, (3) shell spire height, (4) aperture height, and (5) aperture width. We performed frequentist and Bayesian t-tests to determine if there was a significant difference between the two sexes of L. perlucidum on each of the five shell measurements. Additionally, the shell shape was quantified based on nine landmark points using the geometric morphometric approach. We used generalised Procrustes and principal component analyses to test the effects of sex and location on shell shape. The results showed that female shells were larger than male shells across all five measurements (all with p-values < 0.05), but particularly in regards to shell height and shell width. Future taxonomic studies looking to resolve the Leptopoma species’ status should consider the variability of shell size caused by sexual dimorphism.

Species density and morphometric variation of species belonging to Conus (Gastropoda: Conidae) genera in the coastal waters of Ambon Island, Indonesia

Abstract. Tebiary LA, Leiwakabessy F, Rumahlatu D. 2022. Species density and morphometric variation of species belonging to Conus (Gastropoda: Conidae) genera in the coastal waters of Ambon Island, Indonesia. Biodiversitas 23: 1664-1676. Genus Conus Linnaeus, 1758 belongs to the class Gastropods, order Neogastropoda, family Conidae, and its presence in marine ecosystem is influenced by multiple environmental factors. Therefore, this study aims to determine the density and morphometric variations of Conus species in the coastal waters of Ambon Island, Indonesia. This study was carried out from March-April 2021 using the purposive sampling method. The environmental parameters: temperature, salinity, pH, and DO of seawater were measured in-situ, the Conus species were identified at the Central Marine Research Laboratory, the Indonesian Institute of Sciences (LIPI) Ambon, Indonesia while the density data and morphometric variation were determined quantitatively. The results of environmental physico-chemical parameters showed varying values; temperatures ranged from 25.00-29.50oC, salinity 34.00-35.00‰, pH 6.00-7.53, and dissolved oxygen (DO) 4.00-8.00 mg/L. Meanwhile, 7 Conus species was recorded with the density ranging from C. ebraeus with 0.16-0.18 ind/m2, C. rattus, C. sponsalis, and C. lividus ranging from 0.13-0.11 ind/m2, C. monachus, C. muriculatus, and C. coronatus ranging from 0.10 ind/m2. The results of morphometric measurements including shell length (SL), width (SW), thickness (ST), spire height (SH), shell aperture length (SAL), and aperture width (SAW) showed varying values, while the regression analysis results showed that there was a varied relationship between environmental physicochemical parameters and morphometric variations in Conus species. Furthermore, the physico-chemical parameters such as temperature and DO provided the most effective contribution to all morphometric variables.

Molecular phylogenetics and premating isolation in the punctoid land snails of Belau (Republic of Palau, Oceania)

AbstractPacific island land snails exhibit exceptionally high species diversity, morphological diversity, and endemism. Species within superfamily Punctoidea, which contains the Charopidae and Pacific‐endemic family Endodontidae, are among the most morphologically spectacular Pacific endemic land snails. The evolution of Pacific island punctoids remains poorly known, due in part to rampant human‐induced extinction within this group of minute ground‐dwellers. The Belau archipelago (Republic of Palau) with its relatively intact lowland rainforest and limestone karst Rock Islands, is home to many endemic punctoids and presents a unique opportunity to better understand the diversification of one of the most diverse but also imperiled land snail lineages on Pacific islands. For the first time, the diversification of the endemic Pacific punctoid fauna of Belau was studied using Bayesian Inference (BI) and Maximum Likelihood (ML) methods applied to sequences from mitochondrial (COI) and nuclear (ITS2) gene regions. Evolutionary relationships, molecular divergence, disjunct or complex geographic ranges, and ecological similarity among Belau punctoid species, likely reflect species’ long evolutionary history and diversification through geographic isolation. We find no evidence for adaptation in species‐level shifts in spire height within Aaadonta endodontids. We also find preliminary evidence for the evolution of premating reproductive isolation in Semperdon species in sympatry, through the study of apertural teeth. In addition, we report the first new endodontid species from living individuals as well the first new genus record from the Belau archipelago in nearly half a century.

Morphometric Variations of Nerita Lineata Gmelin 1791 in Different Mangrove Age Groups in the Ecosystem

Snail Nerita lineata is a snail that lives in the mangrove ecosystem. This snail is also found in the mangrove ecosystem in the Village of Tongke-Tongke, Sinjai Regency, South Sulawesi. This study aims to provide information about the morphometrics of snails N. lineata. This research was conducted for six months, from April to September 2019. There were three research stations, namely A, B, and C, which were grouped according to mangrove age. group A is mangrove ⩾10 years old, group B is mangrove ⩾20 years old, and group C is mangrove which is rove30 years old. Each station uses a large plot measuring 10m x 10m and inside there are four small plots measuring 0.5m x 0.5m. sampling is done every month. Morphometric measurements using a digital caliper with an accuracy of 0.01 mm and weighing using a digital scale with an accuracy of 0.1 gr. Morphometric parameters observed were shell length (SL), shell width (SW), spire height (SpH), columella length (CL), shell opening width (AW), shell opening length (AL), and snail weight (W). Data were analyzed for correlation and Paired Sample Test using SPSS software. Morphometric snails in mangrove groups A, B, and C are not much different. In the mangrove group A, there are several morphometric parameters that are not correlated with each other. In the mangrove groups B and C, the parameters of shell length (SL) and shell width (SW) do not correlate. The results of the Paired Sample Test showed the significant length of snail (SL) between mangrove A and mangrove B and length of snails in mangrove B and mangrove C. None of the results of paired sample test showed significant snail weight.

Morphometry of the invasive Pomacea spp (Gastropoda: Ampullariidae) from rice fields of Peninsular Malaysia

Morphometry is one of the methods that can be useful in establishing taxon identity. Morphometrics of Pomacea spp in paddy fields of Peninsular Malaysia has not been studied, hence, poorly understood. Morphometric measurement were carried out on shell and operculum characters for six populations of Pomacea spp from paddy fields of peninsula Malaysia to assess ecotype disparity for those characters among the different populations. Results revealed that significant disparity with respect to the assessed characters exists among the populations from different rice ecologies sampled. The highest value for shell length, body whorl height, spire height, aperture length, Aperture width, operculum length and Operculum width were recorded in the Tanjung Karang (Selongor) sampling locality. While the least value for most of these morphometric character were recorded from Tanjung Piandang locality (Perak). It could be concluded that the morphometric characters measured vary independently among the populations measured and is predicted among others factors to be governed by intensity of paddy cultivations rather than geographical gradients. The implications of this finding especially with respect to their management as pest of paddy were discussed.

Size distribution of Strombus luhuanus Linnaeus, 1758 in Oma coastal waters, Central Maluku, Eastern Indonesia

Strombus luhuanus is a marine mesogastropod known as strawberry conch belongs to the Strombidae family. This species is consumed by the coastal community in Maluku province and collected by people at various shell size. The objective of this research was to determine the temporal size distribution and the size difference between its sexes. Sampling was conducted in Oma coastal water, Central Maluku, Eastern Indonesia. A specimen of S. luhuanus collected randomly during low tide from April to July 2018. Some characters of S. luhuanus were measured including shell length, shell width, spire height, and lip thickness. The result of this research showed that shell length of this species varied between 30.81 mm and 55.20 mm; the shell width varied from 16.33 mm to 32.25 mm; its spire height varied between 5.00 mm and 15.20 mm, while the lip thickness varied from 0.10 mm to 5.54 mm. The average of shell length, shell width and spire height of S. luhuanus were high in June sampling period compared to another sampling periods, whereas lip thickness of this species was high in July sampling. Based on its sex, the shell size parameters measured in our study were higher in female specimen than the male one. The size groups of this gastropods were dominated by 38.79-47.39 mm in shell length. Lip thickness of the shell showed that S. luhuanus was in developing stage of growth in this study and S. luhuanus showed sexual dimorphism.

BIOGEOGRAPHIC SHELL SHAPE VARIATION INTROPHON GEVERSIANUS(GASTROPODA: MURICIDAE) ALONG THE SOUTHWESTERN ATLANTIC COAST

Broad-scale latitudinal morphological trends in gastropods along the southwestern Atlantic coast are scant, since the majority of studies have focused on local scales. Here, we evaluate biogeographic shell shape variation in the marine gastropod Trophon geversianus across most of its distributional range, covering 14 degrees of latitude. Samples come from death assemblages which have the potential to unveil biogeographic patterns along spatio-temporal scales and are not affected by short-term volatility in comparison with living assemblages. We performed morphometric analyses on shells from death assemblages, and compared shape variation between mid-Holocene and modern shells from one southern site. Multivariate analyses identified two morphotypes matching the biogeographic regions of the Argentine Sea that segregates a warm-temperate from a cold-temperate zone. The Magellan province morphotype is characterized by a larger shell, lower spire height, and higher aperture length than the Argentinean province morphotype. This change in shell shape is significantly correlated to sea surface temperature, even after accounting for spatial autocorrelation, which could be indirectly influencing intraspecific morphoclines via shifts in growth rates. On the other side, shell size and shape variations were also detected (size increase over recent geological time) between mid-Holocene and modern specimens at the Beagle Channel, which could be attributed to paleoenvironmental changes and to shifts in predator-prey relationships. Our study illustrates the usefulness of death assemblages for revealing large-scale patterns of shell-shape variability in mollusk species, and highlights the spatial coincidence of intraspecific morphological differentiation with the transition zone between biogeographic provinces of the Argentine Sea.

Land snails of Leptopoma Pfeiffer, 1847 in Sabah, Northern Borneo (Caenogastropoda: Cyclophoridae): an analysis of molecular phylogeny and geographical variations in shell form.

Leptopoma is a species rich genus with approximately 100 species documented. Species-level identification in this group has been based on shell morphology and colouration, as well as some anatomical features based on small sample sizes. However, the implications of the inter- and intra-species variations in shell form to the taxonomy of Leptopoma species and the congruency of its current shell based taxonomy with its molecular phylogeny are still unclear. There are four Leptopoma species found in Sabah, Borneo, and their taxonomy status remains uncertain due to substantial variation in shell forms. This study focuses on the phylogenetic relationships and geographical variation in shell form of three Leptopoma species from Sabah. The phylogenetic relationship of these species was first estimated by performing Maximum Likelihood and Bayesian analysis based on mitochondrial genes (16S rDNA and COI) and nuclear gene (ITS-1). Then, a total of six quantitative shell characters (i.e., shell height, shell width, aperture height, aperture width, shell spire height, and ratio of shell height to width) and three qualitative shell characters (i.e., shell colour patterns, spiral ridges, and dark apertural band) of the specimens were mapped across the phylogenetic tree and tested for phylogenetic signals. Data on shell characters of Leptopoma sericatum and Leptopoma pellucidum from two different locations (i.e., Balambangan Island and Kinabatangan) where both species occurred sympatrically were then obtained to examine the geographical variations in shell form. The molecular phylogenetic analyses suggested that each of the three Leptopoma species was monophyletic and indicated congruence with only one of the shell characters (i.e., shell spiral ridges) in the current morphological-based classification. Although the geographical variation analyses suggested some of the shell characters indicating inter-species differences between the two Leptopoma species, these also pointed to intra-species differences between populations from different locations. This study on Leptopoma species is based on small sample size and the findings appear only applicable to Leptopoma species in Sabah. Nevertheless, we anticipate this study to be a starting point for more detailed investigations to include the other still little-known (ca. 100) Leptopoma species and highlights a need to assess variations in shell characters before they could be used in species classification.

On the use of spires for generating inflow conditions with energetic coherent structures in large eddy simulation

ABSTRACTWhile it has long been a practice to place spires near the inlet of a wind tunnel to quickly develop a turbulent boundary layer with similarities to an atmospheric boundary layer, this has not been the case for creating turbulent boundary layer inflow in large eddy simulations (LESs) of turbulent flows. We carry out LES with the curvilinear immersed boundary method to simulate the flow in a wind tunnel with a series of spires in order to investigate the feasibility of numerically developing inflow conditions from a precursory spire LES and assessing the similarities of the turbulence statistics to those of an atmospheric boundary layer. The simulated mean velocity field demonstrates that a turbulent boundary layer with height equal to the spire height develops very quickly, within five spire heights downstream. The major attribute of using spires for precursory simulations is the spatially evolving coherent structures that form downstream of the spires offering a range of length scales at both the vertical and streamwise directions allowing multiple turbulent inflow conditions to be extracted from a single simulation. While the distribution of length scales far from the spires resembles an atmospheric boundary layer, some turbulence statistics have some significant differences.

Morfometric Variations and Long Weight Relationships Red Eye Snail (Cerithidea obtusa)

Red Eye Snail (Cerithidea obtusa) is one species of marine gastropod utilized by coastal communities as a source of animal protein other than fish. Cerithidea obtusa is exploited with varying sizes. This research was conducted at intertidal zone of Pulau Tebing Tinggi beach, Meranti Island regency, Riau from May to June 2017. The objective of the research was to analyse morphometric variation and long-term relationship of Cerithidea obtusa. Samples of Cerithidea obtusa were randomly collected and morphometric parameters measured included shell length, shell width, spire height, shell opening length, shell opening width, and shell depth using digital calipers. The results showed that the long shell of Cerithidea obtusa varied between 21-43 mm, while the width of the shell varied between 13-24 mm. Cerithidea obtusa has a low spire with an oval body shape based on the ratio of shell length to shell width parameters, spire height, shell opening length, shell opening width and shell depth. The relative growth pattern of Cerithidea obtusa is negative allometric.

Local adaptation and embryonic plasticity affect antipredator traits in hatchling pond snails

Summary The biology of induced defences in very early life history stages is poorly understood in freshwater invertebrates, but may be equally, if not more, important than later stages in influencing population dynamics and survival. Here, we investigated how exposure of embryos of the pond snail Lymnaea stagnalis to predator kairomones altered traits associated with protection (crawl out behaviour and shell size) in hatchling snails. We also investigated whether levels of plasticity were influenced by habitat of origin by comparing reaction norms from sites with different levels of predation risk: three high risk (predatory fish present) and three low risk (predatory fish absent). F2 embryos from snails from each population were exposed to kairomones from a predatory fish (Tinca tinca) or control conditions for their entire development up to the point of hatching. Their avoidance behaviour and size (spire height) were then measured 1 day and 7 days after hatching. One day post‐hatching, levels of predator avoidance, primarily time spent at the water line, were significantly greater in high‐risk versus low‐risk populations; however, avoidance was also increased in hatchling snails exposed to predator cues as embryos, compared with those developing in control conditions. Snails exposed to predator cues during development were smaller, and there was a strong negative relationship between size and avoidance behaviour, suggesting a trade‐off or trait compensation between growth and behaviour. At 7 days post‐hatching, a similar pattern in avoidance behaviour was found, with increased avoidance in snails from high‐risk habitats and in those exposed to predator kairomones during their development. The primary avoidance response switched to crawling above the waterline at 7 days post‐hatching. There was no significant difference in shell size between treatments, suggesting that predator‐exposed snails had exhibited ‘catch‐up’ growth. This enhanced investment in growth between 1 day and 7 days post‐hatching was positively correlated with elevated avoidance behaviour across treatment groups, demonstrating that snails switched to trait co‐specialisation of defence traits. During the first few days post‐hatching, snails alter the type of avoidance behaviour and also the relationship between morphological and behavioural defence traits. The degree of expression of these defensive traits in hatchling snails is influenced by both their developmental environment and local adaptation to their predation habitat that may have large implications for survival.

Allometric and trophic effects on shell morphology of Pomacea canaliculata (Caenogastropoda, Ampullariidae) from a geometric morphometrics viewpoint

Pomacea canaliculata, an invasive apple snail native to South America, is a serious pest of aquatic crops in several parts of the world. The origin of inter-population variation in shell shape is thought to be both genetic and environmental but the reaction norms to specific environmental factors are still poorly understood. Our aims were to analyze the existence of direct and indirect (allometric) effects of food availability (FA) on the shape of young adults of P. canaliculata. Full sibling hatchlings were reared under different levels of FA. Nine landmarks and 10 semi-landmarks were determined on photographs of mature shells and analyzed using geometric morphometrics. In both sexes significant allometry was found: a decrease in the spire height in both sexes, and an increase of the aperture size in males and of the last whorl in females. When this allometric component was removed a relationship between size-corrected shape and FA was found only in females, which were more globose and had a larger aperture when grown under high FA. This effect may be explained by the faster growth of the reproductive organs and the thinner shells of the best fed females.

Sexual Dimorphism in the Shell Shape of the Golden Apple Snail, Pomacea canaliculata (Lamarck) Using Geometric Morphometric Analysis

It has been accounted that the extent of sexual dimorphism in Pomacea canaliculata, a serious rice pest in Asia, has caused considerable taxonomic confusion. This study was conducted to explore possible sexual shell dimorphism in P. canaliculata by the aid of geometric morphometric measurements, since traditional measurements have problems in terms of accuracy. Relative Warp Analysis and Discriminant Function Analysis have been used in the study to determine patterns of sexual shell dimorphism in the golden apple snail. Results demonstrated sexual differences in size, spire height, and shell opening. These morphological differences could be attributed to ecological responses of the gastropod. The results clearly indicate that geometric morphometric methods are useful in detecting subtle differences between sexes.

PARATICINELLA N. GEN. AND TAXONOMIC REVISION OF TICINELLA BEJAOUAENSIS SIGAL, 1966

Based on examination of the type material deposited by Jacques Sigal at the Musee National d’Histoire Naturelle in Paris, we have validated the hypothesis of Randrianasolo and Anglada (1998) that the holotype and paratype of Ticinella bejaouaensis Sigal 1966 belong to two different species, the distributions of which do not overlap. Indeed, the holotype is of late Albian age and from Madagascar whilst the paratype is of a latest Aptian age and from Tunisia. Sigal’s paratype is here confirmed to be the holotype of the species eubejaouaensis Randrianasolo and Anglada, 1998. It displays a distinctive wall texture bearing perforation cones that coalesce to form irregularly arranged rugosities and ridges, which tend to parallel the periphery. In addition, flaps may cover the umbilical area. However, it lacks true umbilical supplementary apertures and therefore cannot be included in the genus Ticinella Reichel, 1950. The new genus Paraticinella , with Paraticinella eubejaouaensis as the type species, is here formalized to accommodate uppermost Aptian trochospiral individuals with a wall texture bearing perforation cones, rugosities, and ridges in patterns paralleling the margin, and possessing an umbilical cover-plate. Paraticinella eubejaouaensis evolved from Hedbergella trocoidea in the upper Aptian. The evolutionary trend is exemplified by the increasing number of chambers, by flattening of the spire height, by widening of the umbilicus with the appearance of a cover-plate, by acquisition of well-developed ridges on wall surfaces, and by the appearance of weakly developed infralaminal accessory apertures in later specimens of P. eubejaouaensis . A close study of the holotype of Ticinella bejaouaensis Sigal, 1966 reveals a substantial similarity in morphology and wall structure with Ticinella roberti and a lack of distinguishing criteria between the two species. Consequently, the species Ticinella bejaouaensis is invalidated and is considered to be a junior synonym of T. roberti . A third species was observed associated with Ticinella roberti and Biticinella breggiensis in Madagascar and Spain, and it is attributable to the genus Ticinella based on the presence of true umbilical supplementary apertures and a typical Ticinella wall structure (muricate to coarsely pustulose), while in gross morphology, it resembles Paraticinella eubejaouaensis . We have named this new taxon Ticinella moulladei . It differs from T. roberti by its thinner test, more numerous chambers, and wider umbilicus. Finally, the last zone of the uppermost Aptian must be renamed the Paraticinella eubejaouaensis Zone to replace Ticinella bejaouaensis , which is now considered to be an invalid taxon.

Shell shape and habitat use in the North-west Pacific land snail Mandarina polita from Hahajima, Ogasawara: current adaptation or ghost of species past?

The endemic land snail genus Mandarina of the Ogasawara Islands provides an excellent model system to investigate adaptive radiation. Previously, it has been shown that coexisting species of the islands segregate by microhabitat, so that they are either predominantly found on the ground in relatively wet and sheltered sites, dry and exposed sites, or else are arboreal. Moreover, shell morphology correlates with microhabitat, so that species in wet and sheltered sites tend to have high-spired shells with a high aperture, and those in dry and exposed sites tend to have relatively low-spired shells with a wide aperture. We have now found that on Hahajima, Mandarina polita have variable shell morphology, and there is a correlation between morphology and the depth of leaf litter, as well as the presence/absence of other terrestrial species. Specifically, when high-spired terrestrial Mandarina ponderosa is present, M. polita tend to be low-spired and have a large aperture, indicative of character displacement. When M. ponderosa is absent, the shell shape of M. polita is much more variable, the overall spire is higher, individuals are found in deeper litter, and there is a strong correlation between litter depth and spire height. We argue that these patterns are due to local adaptation, but it remains possible that they are an artefact due to the ‘ghost of species past’. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 149–159.

Morphological variability of Globorotalia menardii (planktonic foraminifera) in two DSDP cores from the Caribbean Sea and the Eastern Equatorial Pacific

Variability in the test of Globorotalia menardii during the past 8 million years has been investigated at DSDP Site 502A (Caribbean Sea) and DSDP Site 503A (Eastern Equatorial Pacific). Measurements were made of spire height (∂x), maximum diameter (∂y), the tangent angles of the upper and lower peripheral keels (Φ1, Φ2, respectively), the number of chambers in the final whorl, and the area of the silhouette in keel view. Four morphotypes alpha, beta, gamma, and delta were distinguished. Morphotype alpha was found in strata ranging in age from the Late Miocene through the Holocene. It shows a continuous increase in ∂x and ∂y until the Late Pleistocene. During and after the final closure of the ancient Central American Seaway (between 2.4 Ma and 1.8 Ma) there was a rapid increase in the area of the test in keel view. At the Caribbean Sea site, morphotype beta evolved during the past 0.22 Ma. It is less inflated than alpha and has a more delicate test. In the morphospace of ∂x vs. ∂y, morphotypes alpha and beta can be distinguished by a separation line ∂y = 3.2 * ∂x - 160 (∂x and ∂y in µm). Plots of morphotype alpha are below that line, those of beta are above it. Morphotype alpha is taken to be Globorotalia menardii menardii Parker, Jones & Brady (1865) and includes G. menardii 'A' Bolli (1970). Morphotype beta is identified as G. menardii cultrata (d'Orbigny). Morphotypes gamma and delta are extinct Upper Miocene to Pliocene forms which evolved from morphotype alpha. They have a narrower Φ1 angle and more chambers (≥7) than morphotype alpha commonly with 5 to 6 chambers (7 in transitional forms). In contemporaneous samples morphotype delta can be distinguished from gamma by a smaller value of Φ1 and 8 or more chambers in the final whorl. Morphotype gamma is taken to be G. limbata (Fornasini, 1902) and includes the junior synonym G. menardii 'B' Bolli (1970). Morphotype delta is G. multicamerata Cushman & Jarvis (1930). With the exception of the Late Pleistocene development of G. menardii cultrataonly in the Caribbean the morphological changes of G. menardii at DSDP Sites 502A and 503A are similar. The development from the ancestral G. menardii menardii of the G. limbata - G. multicamerata lineage during the Pliocene and of G. menardii cultrata during the Late Pleistocene suggests responses at the two sites to a changing palaeoceanography during and after the formation of the Isthmus of Panama.

Selected shell characters as criteria of distinguishing between Ventrosia ventrosa (Montagu, 1803) and Peringia ulvae (Pennant, 1777) (Gastropoda: Prosobranchia: Hydrobiidae)

Some shell characters of Ventrosia ventrosa (Montagu) and Peringia ulvae (Pennant) can be used to distinguish between the two taxa. Out of 12 initially analysed characters, 3 (shell width, spire height, aperture height) were selected as sufficient to describe the shells and distinguish between the species. Discriminant analysis made it possible to construct two classifying functions. Though the results confirm the difficulties implied in conchological identification of V. ventrosa and P. ulvae, the high proportion of correct species distinction (over 90%) based on the three characters invites further research.