Anchor Shaft Research Articles

The pull-out capacity of torpedo anchor in clay considering the full opening cavity

Torpedo anchors are increasingly being considered for mooring floating facilities in deep waters owing to their efficient and economical installation. The anchor was released from a specified height above the seabed to allow it to gain velocity as it fell freely into the water before penetrating the seabed. A cavity was formed above the anchor shaft after the anchor installation. The formation of this post-installation cavity is largely dependent on the soil strength conditions and affects the anchor capacity after installation. However, there is a lack of understanding regarding the formation mechanisms of the cavity and its effect on the bearing capacity of a torpedo anchor. Thus, this study focuses on the effects of the post-installation cavity on the bearing capacity of the torpedo anchor. The impact of a fully open post-penetration cavity on both the vertical and inclined bearing capacity of a torpedo anchor without fins was investigated using the Coupled Eulerian–Lagrangian (CEL) method in ABAQUS with three-dimensional large deformation finite element (LDFE) analysis. A method for evaluating the vertical bearing capacity of a torpedo anchor, considering the effect of a post-installation cavity, was proposed. This study provides insight into the installation effect on the bearing capacity of torpedo anchors.

Three-dimensional finite element analysis for uplifting independent helix plate anchor in uniform clay

Three-dimensional finite element analysis offers a more realistic representation of the geometry of the helix plate anchor. For the helical anchor with a single helix plate or multiple helix plates whose spacing distance is large between each plate, each helix plate behaves independently during uplifting. Although numerous studies have estimated the uplift capacity factor of independent circular plate anchors in uniform clay, rare research comprehensively considers the effects of helix pitch, anchor shaft, and soil rigidity on estimating the uplift capacity factor for independent helix plate anchors. In this paper, three-dimensional finite element analyses were conducted to investigate the impacts of helix pitch, anchor shaft, and soil rigidity on estimating the uplift capacity factor of independent helix plate anchors with shafts in uniform clay. Analysis results demonstrated that the increasing helix pitch and anchor shaft diameter could significantly decrease the uplift capacity factor. The change in the soil rigidity also influenced uplift capacity factor estimation. Therefore, determining the uplift capacity factor should comprehensively account for the effects of embedment depth, helix pitch, anchor shaft, soil rigidity, and overburden pressure. In this study, a procedure was suggested for creating design guidelines to estimate uplift capacity factors for independent helix plate anchors.

Numerical investigations of hydrodynamic performance of dynamically installed anchors subjected to current considering anchor geometric effects

Dynamically installed anchor is an innovative and cost-effective technology in marine foundation engineering. However, most of the existing researches on the hydrodynamic characteristics of dynamically installed anchors are limited to their free-fall installation performance in water without considering the action of marine environmental loads such as current. Therefore, this study aims to investigate the hydrodynamic performance of dynamically installed anchors subjected to current in a systematical manner. A complete three-dimensional CFD model is firstly established using “dynamic model analysis” method. Then, the effects of anchor geometric characteristics on the installation efficiency (i.e., penetration velocity and drag coefficient) and installation positioning accuracy (i.e., lateral velocity and displacement, and inclination angle) of the anchors subjected to current are systematically studied using the established CFD model. The influences of current velocity, current direction and geometric characteristics including anchor shaft geometry and anchor fin geometry on the hydrodynamic characteristics of anchor are discussed. Based on the obtained findings, some practical design recommendations are given, and a simple semi-empirical method for estimating the falling velocity and inclination angle of dynamically installed anchor subjected to current considering anchor geometric effects is finally proposed, which may benefit the engineering design of dynamically installed anchors.

Analytical model of the shear behaviors of bolted rough joints based on the dilation effect and surface abrasion

Rock bolts have been widely employed on slopes as a reinforcement measure. Modeling the shear mechanical behaviors of bolted rock joints is very complicated due to the complex factors that affect the axial and shear forces on the bolts. The rough surface of the joint surface undergoes a dilation effect and morphological abrasion under shearing. However, existing analysis models do not fully consider these effects. This study proposes an analytical model for predicting the shear behaviors of bolted rough joints. The model considers the relationship between the dilation effect and the bolt deformation and the influence of joint surface abrasion on the attenuation of the internal friction angle. Moreover, the axial force development is corrected at a bolt installation angle of 90 degrees, and the effect of the initial normal stress of the joint surface on the deformation and fracture of the bolt is also considered. The analysis model successfully predicts the shear load-shear displacement curve of the anchoring joint and the change curve of the anchor shaft force. The analysis model is verified by an indoor direct shear test. The validation shows that the proposed model can effectively describe the deformation characteristics of the bolts in shear tests.

The Helical Anchor Type with Application as a Horizontal Drainage Equipment for Slope Protection

Helical anchors, sometimes referred to as screw anchors, screw piles, and helical piles, are a steel screw-in piling and ground anchoring system used for building deep foundations. Screw piles are manufactured using varying sizes of tubular hollow sections for the pile or anchor shaft. This paper presents an innovation of the helical anchor for horizontal drains, a form of subsurface drainage systems for slope protection. To address the adverse effect of groundwater, an expansion of the application of the helical anchor structure in civil engineering is needed, and new drainage solutions are being considered. The features of the helical anchor type for horizontal drainage equipment, analyses of some of its advantages, and conditions of application are presented. Generally, a helical anchor for horizontal drainage is convenient for installation, maintenance, or removal, and is effective for both horizontal drainage and for anchoring the revetment. It is also a typical construction in drainage works, generally performed by a cranking handle or a rotary-percussion-type drilling machine. The helical anchor pipe for horizontal drainage has many segments with joints using a cranking hand for installation and is quite effective where the installation space is narrow or there is no machine. In particular, the installation of this equipment differs significantly from other drilling methods because it can be driven into a sand layer without a hole wall.

Vertical Pullout Behaviour of a Torpedo Anchor Vertically in Stiff-Over-Soft Cohesive Soil Bed

This paper reports the results from a large deformation finite element (LDFE) model to provide insights into the vertical pullout behaviors of torpedo anchors in stiff-over-soft soil beds. 10 sets of numerical data were obtained by varying the top layer thickness, soil shear strength of the stiff-over-soft soil bed, tip embedment depth ratio, and pullout speed. The tip embedment depth ratio of the torpedo anchor (the ratio of the embedment depth at anchor tip to the anchor shaft length) varied from 1.48 to 2.91. Soil flow characteristic was discovered by the finite element analysis. The observation of soil flow characteristics provided deep insight with the interaction between the torpedo anchor and its surrounding soil.

Numerical study on pull-out capacity of torpedo anchors in clay

This paper reports the results from dynamic finite-element analyses undertaken to provide insight into the behaviour of torpedo anchors during pullout in non-homogeneous clay. The results were validated against field data prior to undertaking a parametric study, exploring the relevant range of parameters in terms of installation effect, impact velocity, anchor geometry, padeye position, pullout angle. Installation method (e.g. quasi-static and dynamic installation) has shown significant influence on the vertical pullout capacity, but that influence reduced to marginal for lateral pullout. The inclined pullout capacity was dictated by the anchor weight and fully mobilised anchor-soil contact surface area and consequently the capacity increased with increasing the number of fins. Due to the lower weight and total surface area, the 45° (at the padeye) pullout capacity of the finless anchor was 29% of that of the considered four-fin anchor. The results showed that this percentage can be increased to 83% by shifting the padeye location of the finless anchor to 0·56 times the anchor shaft length from the top. Anchor capacity under inclined pullout loading was presented as failure envelopes expressed in terms of dimensionless vertical and horizontal components, which lied between the envelops developed for piles and embedded foundations.

Monogenean anchor morphometry: systematic value, phylogenetic signal, and evolution.

Background. Anchors are one of the important attachment appendages for monogenean parasites. Common descent and evolutionary processes have left their mark on anchor morphometry, in the form of patterns of shape and size variation useful for systematic and evolutionary studies. When combined with morphological and molecular data, analysis of anchor morphometry can potentially answer a wide range of biological questions.Materials and Methods. We used data from anchor morphometry, body size and morphology of 13 Ligophorus (Monogenea: Ancyrocephalidae) species infecting two marine mugilid (Teleostei: Mugilidae) fish hosts: Moolgarda buchanani (Bleeker) and Liza subviridis (Valenciennes) from Malaysia. Anchor shape and size data (n = 530) were generated using methods of geometric morphometrics. We used 28S rRNA, 18S rRNA, and ITS1 sequence data to infer a maximum likelihood phylogeny. We discriminated species using principal component and cluster analysis of shape data. Adams’s Kmult was used to detect phylogenetic signal in anchor shape. Phylogeny-correlated size and shape changes were investigated using continuous character mapping and directional statistics, respectively. We assessed morphological constraints in anchor morphometry using phylogenetic regression of anchor shape against body size and anchor size. Anchor morphological integration was studied using partial least squares method. The association between copulatory organ morphology and anchor shape and size in phylomorphospace was used to test the Rohde-Hobbs hypothesis. We created monogeneaGM, a new R package that integrates analyses of monogenean anchor geometric morphometric data with morphological and phylogenetic data.Results. We discriminated 12 of the 13 Ligophorus species using anchor shape data. Significant phylogenetic signal was detected in anchor shape. Thus, we discovered new morphological characters based on anchor shaft shape, the length between the inner root point and the outer root point, and the length between the inner root point and the dent point. The species on M. buchanani evolved larger, more robust anchors; those on L. subviridis evolved smaller, more delicate anchors. Anchor shape and size were significantly correlated, suggesting constraints in anchor evolution. Tight integration between the root and the point compartments within anchors confirms the anchor as a single, fully integrated module. The correlation between male copulatory organ morphology and size with anchor shape was consistent with predictions from the Rohde-Hobbs hypothesis.Conclusions. Monogenean anchors are tightly integrated structures, and their shape variation correlates strongly with phylogeny, thus underscoring their value for systematic and evolutionary biology studies. Our MonogeneaGM R package provides tools for researchers to mine biological insights from geometric morphometric data of speciose monogenean genera.

Numerical investigation of dynamic installation of torpedo anchors in clay

This paper reports the results from three-dimensional dynamic finite element analysis undertaken to provide insight into the behaviour of torpedo anchors during dynamic installation in non-homogeneous clay. The large deformation finite element (LDFE) analyses were carried out using the coupled Eulerian–Lagrangian approach, modifying the simple elastic-perfectly plastic Tresca soil model to allow strain softening, and incorporate strain-rate dependency of the shear strength using the Herschel–Bulkley model. The results were validated against field data and centrifuge test data prior to undertaking a detailed parametric study, exploring the relevant range of parameters in terms of anchor shaft length and diameter; number, width and length of fins; impact velocity and soil strength. The anchor velocity profile during penetration in clay showed that the dynamic installation process consisted of two stages: (a) in Stage 1, the soil resistance was less than the submerged weight of the anchor and hence the anchor accelerated; (b) in Stage 2, at greater penetration, frictional and end bearing resistance dominated and the anchor decelerated. The corresponding soil failure patterns revealed two interesting aspects including (a) mobilization of an end bearing mechanism at the base of the anchor shaft and fins and (b) formation of a cavity above the shaft of the installing anchor and subsequent soil backflow into the cavity depending on the soil undrained shear strength. To predict the embedment depth in the field, an improved rational analytical embedment model, based on strain rate dependent shearing resistance and fluid mechanics drag resistance, was proposed, with the LDFE data used to calibrate the model.

Anchor Fitted with Special Fin for Soil Reinforcement

In order to ensure that anchored soil retention systems are more stable and free from failure, suitable anchors are required. A new technique using anchors with fins were investigated, particularly for mechanically stabilized earth. An experimental laboratory investigation on the behaviour of anchors with fins by using various shapes, sizes, arrangements and lengths were presented. The main purpose of this study is to investigate the load-displacement relationship of pullout anchors with fins embedded in sand. A rectangular model tank with dimensions 0.6 m length, 0.5 m width and 0.3 m high was designed. Models of 15 types of anchors of different lengths (0.3 m, 0.4 m and 0.5 m) with fins using different and various types of lengths, sizes and arrangements embedded in sand, were experimented with . The testing program included 45 tests embedded in dry sand. The experiment was conducted in a soil laboratory at a scale of 1:10. The fin was placed at the end of the anchor shaft that abuts the failing structure which prevents further movement. It was concluded that the size, shape and angle of the fin influenced the pullout capacity of the anchor. Finally, selected anchors were recommended based on their superior performance.

Behavior of pressure-grouted anchors in gravel

This study consisted of field tests conducted on nine vertical and three inclined low-pressure-grouted anchors to investigate their behavior in gravel. An anchor can be categorized as a deep anchor when the overburden depth (free length) Z exceeds 8D (D is the diameter of the anchor). The shape of the heave on the ground surface of a shallow anchor is similar to a normal distribution curve. The extended diameter of the heave was between 170 and 300 cm, which could be divided into two zones, primary and secondary, based on the failure mode of the ground. As the fixed length of a shallow anchor increased, the extended diameter also increased. The ultimate load on an anchor increased with the free length and, to a greater degree, with the fixed length of an anchor: a fixed length of only 3 m generated an ultimate load of over 1100 kN. However, the permissible load, determined from the creep coefficient, is inapplicable for short anchors in gravel. The earth pressure coefficient K of vertical anchors was approximately 29 and for an anchor shaft inclined at 25º it was approximately 17.7.

Numerical Modeling of Earth Structures: Frictional Anchors in Sand

This research performed a series of triaxial tests on sandy specimens to obtain the parameters needed for a constitutive model. The model is capable to simulate the strain hardening/softening and the volumetric dilation of sandy soil during stressing. The model and the related parameters were then employed in the commercial software FLAC2D to analyze the uplift behavior of various frictional anchors in sandy soil. Analysis results indicate that the friction stress along the fixed end of the anchor with a long fixed length exhibits progressive yielding under not only for a tension but also for a compression anchor. The progressive yielding behavior could be eliminated using a compound anchor because of the upward and downward transfer of load within the anchor shaft from the anchorage body. Therefore, a compound anchor can generate a higher anchorage capacity of all frictional anchors.

Model Test of Mechanical Characteristics of Cantilever Retaining Wall with Mutual Anchor

In order to analysis force characteristics and changes of the anchor tension during the process of filling soil of the pull cantilever retaining wall, a model test is designed for research. The test mainly monitors basal earth pressure, lateral earth pressure of the retaining wall, anchor shaft force, lateral displacement of the retaining wall.

Three new species of Protogyrodactylus Johnston & Tiegs, 1922 (Monogenoidea: Dactylogyridae) from the gills of the longtail silverbiddy Gerres longirostris (Teleostei: Gerreidae) in the Red Sea

Twenty-one specimens of the longtailed silverbiddy Gerres longirostris (Gerreidae) were examined for dactylogyrid parasites from the Nabq Managed Resource Protected Area, Ras Mohammed National Park (Red Sea) near Sharm El-Sheikh, South Sinai, Egypt. The diagnosis of Protogyrodactylus Johnston & Tiegs, 1922 was amended, and three new species, P. federicae n. sp., P. zullinii n. sp. and P. alatus n. sp., were recovered and described; the prevalence of each species was 100%. P. federicae most closely resembled P. alienus Bychowsky & Nagibina, 1974, but differed from it by possessing two anteromedial projections on the ventral bar, a claw-like ventral anchor sclerite and spatulate dorsal bars. P. zullini was most similar to P. quadratus Johnston & Tiegs, 1922, from which it differed by having a distal hook on the superficial root of the dorsal anchor, an evenly curved ventral anchor shaft and point, and a flange on the bulbous base of the male copulatory organ. P. alatus was closest to P. youngi Bychowsky & Nagibina, 1974, from which it differed by having delicate anchors and two prominent anteromedial processes on the ventral bar.

Variability of the opisthaptoral hard parts ofGyrodactylus callariatis Malmberg, 1957 (Monogenea: Gyrodactylidae) from Atlantic codGadus morhua L. in the Oslo Fjord, Norway

The present study describes the variability of the opisthaptoral hard parts ofGyrodactylus callariatis Malmberg, 1957 infesting juvenile Atlantic codGadus morhua L. in the Oslo Fjord, Norway. Samples were taken monthly or bimonthly from January 1993 to July 1994. The length of the 14 characters measured varied considerably throughout the period, and showed a significant regression on the water temperature: as the water temperature increased the length of the hard parts decreased andvice versa. There were no significant differences in the size of the hard parts between young worms (without penis) and older worms (with penis). Some of the characters (especially the anchor shaft) from parasites located on the skin and fins were significantly longer than those of parasites located in the oral cavity, pharynx and gills. Generally, the variation in the shape of the hard parts was small; the anchor root, ventral bar membrane and ventral bar processes were the most variable parts. The shape of the hard parts did not vary as a consequence of seasonal changes in the water temperature, age of the worms or site on the host.

A Tractor-Powered Method for Installing Earth Anchors during Fence Construction

Fencing is an important tool for managing rangelands. However, the cost of conventional fencing is often prohibitive for anything other than boundary or important cross fences (Moore et al. 1968). Suspension fences cost about half as much as conventional fences, and, under many conditions, will turn cattle equally well, last as long, and require less upkeep (McNamee and Kinne 1965). A suspension fence requires strong comer assemblies. A typical comer is double braced with the first brace post guyed to a ‘deadman” (a large object such as a rock or section of post) buried 60 cm deep midway between the corner and first brace post. Installing a deadman is hard, time-consuming work. Under most soil conditions it takes one man approximately 45 minutes per deadman if a power auger is used to dig the hole. This paper describes the adaptation of a tractor-powered post hole digger to screw earth anchors into the soil for use as a deadman, thus reducing the installation time per deadman from 45 to 10 minutes. It also reports on the suitability of earth anchors for holding fence-corner assemblies. The use of a tractor to install screw-in earth anchors requires an adapter to transmit the turning force of the auger power head to the earth anchor. The adapter (Fig. 1) fits on the power head in place of the auger and holds the eye of the earth anchor so that the power head can screw the anchor into the soil. The materials needed to construct the adapter are readily available ih most communities from some of the larger hardware stores (Fig. 1). The earth anchor used with the adapter shown in Figure 1 had an 1 1 / 16-inch (18 mm) rod, a 6-inch (15 cm) helix, and an overall length of 48 inches (122 cm). If an anchor with a different sized eye or rod were used, the dimensions of the adapter would need to be adjusted accordingly. Also, if the shaft of the power-head were different in size than the one used, a different sized adapter sleeve would be needed (Fig. 1). Earth anchors should be lined up and installed before the posts are set; this allows room to operate the tractor. The anchor is started perpendicularly to the ground and turned until the helix is covered by the soil surface. The anchor shaft is then angled towards

Dactylogyrids from North American Cyprinids of the Genus Nocomis: The Limulus and the Mollis Groups

Two dactylogyrid (Monogenea) morphologically similar groups, limulus and mollis, parasitizing the North American cyprinid fish genus Nocomis are reported. Three new species are described: Dactylogyrus flagristylus sp. n. taken from N. asper, N. biguttatus, and N. effusus; D. malleolus sp. n. taken from N. micropogon and N. leptocephalus leptocephalus; and D. mollis sp. n. taken from N. raneyi and N. micropogon. D. limulus Rogers, 1967, was recovered from N. 1. bellicus, and for the first time from N. 1. interocularis and N. 1. leptocephalus. Known distribution and parasite phylogeny are discussed. Two dactylogyrid groups, reciprocus and bellicus, parasitizing gills of the cyprinid fish genus Nocomis were reported previously (Chien, 1971, 1974). The present study discusses two new groups: the limulus group, including Dactylogyrus limulus Rogers 1967, and two new species; and the mollis group including only a new species. A total of 623 parasites were obtained from 781 host fish examined. Host species are those discussed by Lachner and Jenkins (1967, 1971a, b) and Lachner and Wiley (1971). Methods are those used by Chien (1971). Known distributions are listed and phylogeny of the parasites is discussed. Measurements are in microns. The average is followed by the range in parentheses. Hosts were collected from museums in many cases and the following codes used: USNMUnited States National Museum, BM (NH)British Museum (Natural History), R.-River, dr.-drainage, sys.-system. Numerals following the drainage designation denote the number of localities where the particular parasites were collected. DESCRIPTIONS OF DACTYLOGYRUS Diagnosis for the limulus group Eyespots subequal or posterior pair may be larger. Copulatory complex highly modified; cirrus slender, thin-walled; accessory piece composed of several portions, generally a terminal piece. Haptor broadly rounded, densely compacted. Ventral bar Received for publication 26 March 1974. * Supported by the Southeastern Cooperative Fish Disease Project, Rockefeller Foundation RF 65061, and Alabama Cooperative Fishery Unit, Auburn University. t Present address: NUS Corporation, C. W. Rice Division, Manor Oak 2, 1910 Cochran Road, Pittsburgh, Pennsylvania 15220. vestigial. Anchor shaft smoothly curved, gently tapered to point. Shaft 11/2 to 14 times point length. Anchor wings confined to proximal half of shaft. Hooks (except 4A) subequal. Other characteristics similar to bellicus group. Dactylogyrus flagristylus sp. n.

The Influence of Anchor Inclination on Pull-out Resistance of Clays

A theoretical model is described that was used to examine the influence of anchor inclination on pull-out capacity. Use was made of previous general findings for pile shaft adhesion prediction in stiff clays. It is shown that the adhesion available at the anchor shaft – clay interface depends on: (1) the in situ stress state in the ground; (2) anchor inclination; and (3) the initial shear stress existing in the ground in the direction of the anchor shaft. The possible importance of the reported trends is considered.

Studies on Dactylogyrinae (Monogenea) with Descriptions of 24 New Species of Dactylogyrus, 5 New Species of Pellucidhaptor, and the Proposal of Aplodiscus gen. n.

Thirty new and 29 previously described species of Dactylogyrinae are reported from fishes of the southeastern U. S. 1T The new species and their hosts are: Aplodiscus nasalis, gen. et sp. n. from Hypentelium etowanum (Jordan); Dactylogyrus acicularis sp. n. from Moxostoma poecilurum (Jordan); D. arcus sp. n., D. cursitans sp. n., D. lepidus sp. n., D. luxili sp. n., and D. manicatus sp. n. from Notropis chrysocephalus isolepis Hubbs and Brown; D. argenteus sp. n. from Notropis shumardi (Girard); D. caudoluminis sp. n. from Notropis maculatus (Hay); D. cheloideus sp. n. from Rhinichthys atratulus (Hermann); D. crucis sp. n. from Notropis bellus (Hay); D. ericymbae sp. n. and D. julieae sp. n. from Ericymba buccata Cope; D. fungulus sp. n. from Notropis callistius (Jordan); D. hemitremiae sp. n. from Hemitremia flammae (Jordan and Gilbert); D. limulus sp. n. and D. reciprocus sp. n. from Hybopsis bellica (Girard); D. magnus sp. n. from Hybopsis storeriana (Kirtland); D. opsopoeodi sp. n. from Opsopoeodus emiliae Hay; D. ornatus sp. n. from Notropis baileyi Suttkus and Raney; D. parvaccessorius sp. n. from Hybopsis herperi (Fowler), D. plegadus sp. n. from Hyjbopsis amblops (Raf.); D. pronatus sp. n. from Notropis hypselopterus (Gunther); D. venusti sp. n. from Notropis venustus (Girard); D. welakae sp. n. from Notropis welaka Everman and Kendall; Pellucidhaptor eremitus sp. n. from Carpiodes velifer (Raf.); P. orthacis sp. n. from Moxostoma poecilurum (Jordan); P. pterigynus sp. n. from Hypentelium etowanum (Jordan); P. ramulosus sp. n. and P. smithvanizi sp. n. from Minytrema melanops (Raf.). ?f Previously described species found were: Dactylogyrus absidatus Rogers and Mizelle, 1966; D. alabamensis Rogers and Mizelle, 1966; D. anchoratus Wagner, 1857; D. apos Mueller, 1938; D. attenuatus Mizelle and Klucka, 1953; D. aureus Seamster, 1948; D. banghami Mizelle and Donahue, 1944; D. baueri Gussev, 1955; D. bellicae Rogers and Mizelle, 1966; D. bifurcatus Mizelle, 1937; D. bulbus Mueller, 1938; D. bychowskyi Mizelle, 1937; D. confusus Mueller, 1938; D. cornutus Mueller, 1938; D. duquesnei Mueller, 1938; D. extensus Mueller and Van Cleave, 1932; D. formosus Kulwiec, 1927; D. hamatus Rogers and Mizelle, 1966; D. lineatus Mizelle and Klucka, 1953; D. microphallus Mueller, 1938; D. minutus Kulwiec, 1927; D. moorei Monaco and Mizelle, 1955; D. niger Rogers and Mizelle, 1966; D. nuchalis Wood and Mizelle, 1957; D. parvicirrus Seamster, 1948; D. plumbeus Rogers and Mizelle, 1966; D. semotilus Wood and Mizelle, 1957; D. vastator Nybelin, 1924; Pellucidhaptor alabamensis Rogers and Mizelle, 1966. ?[ Aplodiscus gen. n. appears most closely related to Dactylogyrus, but may be distinguished by the absence of a haptoral bar supporting the anchors, absence of anchor wings (filaments), the deep anchor root being an extension of the anchor shaft, and the 4A hooks being larger than in Dactylogyrus. A proposal is made that subfamily diagnosis be emended to include absence of haptoral bars. If The gut of four of the five new species of Pellucidhaptor was observed to be confluent, and P. orthacis was observed to have straight instead of doubly recurved anchor points. All of the Pellucidhaptor species reported herein were observed to inhabit the body rather than the gills. The generic diagnosis is emended to include these characters. [ The generic diagnosis of Dactylogyrus is emended. A ventral bar was observed in all of the new Dactylogyrus species as were the 4A haptoral hooks. The ventral bar is greatly reduced or absent in many specimens, however, and does not warrant upholding Neodactylogyrus Price, 1938. The genus Dactylogyrus was reviewed by Monaco and Mizelle (1955) and a parasitehost:host-parasite checklist presented in addition to describing nine new species. They listed 50 species of Dactylogyrus from North America but the six species described by Kimpel (1939) did not meet the requirements for publication as set forth by the International Rules of Zoological Nomenclature and were declared nomina nuda by Yamaguti (1963). Received for publication 19 September 1966. * Supported by the Southeastern Cooperative Fish Parasite and Disease Project. 501 Wood and Mizelle (1957) described four new species of Dactylogyrus as follows: D. nuchalis from the silvery minnow, Hybognathus nuchalis Agassiz; D. osculus from the dace, Rhinichythys osculus robustus (Rutter); D. rhinichthius from the dace Rhinichthys altratulus meleagris Agassiz; D. semotilus from the creek chub, Semotilus a. atromaculatus