Loose Piles Research Articles

Solving problem of encountering a huge cavern in a TBM drive for water diversion tunnel project in Northern Thailand

AbstractA huge cavern in a zone of thrusted and sheared clastic sedimentary rocks was encountered during drill and blast (D&B) and tunnel boring machine (TBM) excavation of water transfer tunnel in Thailand. The cavern floor made of thick and loose pile of fallen rock blocks hampered the advance of the TBM through it. Because the size of the cavern was large (50 m × 40 m) and the extent of the thickness of the pile of rock blocks could not be precisely determined, the adopted ramification was to solidify a zone of loose rock fragments around the tunnel alignment. This measure is to allow a safe TBM excavation passing the cavern and ensure the long‐term function of the segmented concrete‐lined tunnel to convey water without problem of loss from subsidence damage. The scheme of the solidification consisted of staged grouting that began with polyurethane (PU) foam grouting to form a bottom barrier of the intended cement grout zone. It was followed large void filling by flowable concrete and then cement injection for the remaining smaller voids. The work that took 8 months to complete started with the excavation of a bypass adit to the front of TBM cutterhead as an access to the cavern and the installation of dewatering and ventilation systems to the cavern so that the grouting work could be made.

Condition Monitoring of an Axial Piston Pump on a Mini Excavator

The focus of this paper is to show the process of developing a condition monitoring system for an axial piston pump mounted on a mini excavator. This work outlines some previous condition monitoring work on axial piston pumps but addresses the lack of research conducted on mobile hydraulics. The valve plate of the pump is chosen as a case study to demonstrate varying degrees of wear and damage to represent healthy and faulty pump conditions. The wear and damage of these valve plates is measured using an optical profilometer, and efficiency measurements were conducted to characterize the fault levels. Once the faults were characterized, the mini excavator was introduced and instrumented to demonstrate what parameters were being considered. Next, three duty cycles were introduced: controlled, digging, and different operator cycles. The controlled cycles are a very repeatable condition that eliminated the need of an operator. The digging cycle was more of a realistic cycle where an operator dug into a loose pile of soil. The different operator cycle is the same as the digging cycle, but a different operator was employed. The sensors that proved to be the most useful in detecting valve plate faults were the drain pressure, pump port pressures, engine speed, and pump displacement. Fault detectability accuracies of 100% were achievable under the controlled cycle utilizing the Fine KNN classification machine learning algorithm. The digging cycle could achieve a fault detection accuracy of 93.6% using the same algorithm and sensors. Finally, the cross-compatibility between a model trained under once cycle and using data from another cycle as an input was investigated. This study showed that a model trained under the controlled duty cycle does not give reliable and accurate fault detectability for data run in a digging cycle, below 60% accuracies. However, cross-compatibility may be achievable if more extreme faults are present. This work concluded by recommending a diagnostic function for mobile machines to perform a preprogrammed operation to reliably and accurately detect pump faults.

Variation of Open-Pit Waste Dump Specimens Under Effective Pressure Influence

The waste dump is a giant artificial loose pile body composed of fine, medium, and coarse particle sizes. Rising incidents of landslides caused by overburden pressure and effective pressure are of increasing concern in the open-pit waste dump and, if not well-controlled, are a dangerous threat to the workers, the environment, and the equipment. The purpose of this research is to investigate the connection between effective pressure, porosity, void ratio, and coefficient of permeability and to find their influence in the open-pit waste dump. This study analyzed the mechanical and physical changes of seven different soil samples using consolidation and permeability under consolidation laboratory test. The test samples were subject to a pressure ranging from 100 to 1600 kPa. The effective pressure was found to play a major role in influencing void ratio, porosity, and coefficient of permeability, and waste dump height management and control are of great importance. This study answers the question regarding the correlation between effective pressure, void ratio, porosity, and coefficient of permeability in the open-pit waste dump. Further studies are needed to establish profound relationships and develop preventative measures to keep the waste dump slope stable and safe.

Analysis of Solid-State Luminescence Emission Amplification at Substituted Anthracenes by Host-Guest Complex Formation.

Invited for the cover of this issue are Dietmar Stalke and coworkers from the Georg-August Universität at Göttingen. The image symbolizes the organization of small arenes in the pocket of thiophosphoranyl substituted anthracene like the construction of a stable wall from a loose pile of bricks, shifting the emission to the green and amplifying it by a factor of five. Read the full text of the article at 10.1002/chem.202003017.

An Improved Ground Control Point Configuration for Digital Surface Model Construction in a Coal Waste Dump Using an Unmanned Aerial Vehicle System

Coal production in opencast mining generates substantial waste materials, which are typically delivered to an on-site waste dump. As a large artificial loose pile, such dumps have a special multi-berm structure accompanied by some security issues due to wind and water erosion. Highly accurate digital surface models (DSMs) provide the basic information for detection and analysis of elevation change. Low-cost unmanned aerial vehicle systems (UAS) equipped with a digital camera have become a useful tool for DSM reconstruction. To achieve high-quality UAS products, consideration of the number and configuration of ground control points (GCPs) is required. Although increasing of GCPs will improve the accuracy of UAS products, the workload of placing GCPs is difficult and laborious, especially in a multi-berm structure such as a waste dump. Thus, the aim of this study is to propose an improved GCPs configuration to generate accurate DSMs of a waste dump to obtain accurate elevation information, with less time and fewer resources. The results of this study suggest that: (1) the vertical accuracy of DSMs is affected by the number of GCPs and their configuration. (2) Under a set number of GCPs, a difference of accuracy is obtained when the GCPs are located on different berms. (3) For the same number of GCPs, the type 4 (GCPs located on the 1st and 4th berms) in the study is the best configuration for higher vertical accuracy compared with other types. The principal objective of this study provides an effective GCP configuration for DSM construction of coal waste dumps with four berms, and also a reference for engineering piles using multiple berms.

Role of microtopography in the expression of soil propagule banks on reclamation sites

The legacy propagule banks of salvaged topsoils are excellent sources of plant propagules for reclamation of mine sites; however, earlier studies show that less than 50% of the species found in original propagule banks actually establish. We hypothesize that the expression of this legacy propagule bank is limited by a lack of diversity of microsites and appropriate growing conditions. In an operational‐scale field experiment we manipulated topographical characteristics and substrate materials and explored early vegetation establishment on an east‐ and south‐facing slope. Three different site treatments with different microtopographic characteristics: (1) leveled surface, (2) parallel ridges, and (3) large loose piles were created using salvaged upland and lowland forest floor soil materials. Placing materials in loose hills and providing heterogeneity in substrates more than doubled plant abundance, species richness, and increased the proportion of species that require higher soil moisture. Lower micro‐elevations and northern microaspects of the microtopographic treatments had up to three times higher soil water content and double the species richness. However, the overall slope aspect had a modulating effect on microtopographic positions. The greatest treatment effect of micro‐elevation and microaspect on species richness and plant abundance occurred on the east‐facing slope, while the greatest effect of treatment on the proportion of species requiring higher soil moisture conditions was observed on the south‐facing slope. Variability in microtopography and substrate can create favorable growing conditions at an operational scale and help express a wider range of species from the legacy propagule bank.

The African Photographic Archive: Research and Curatorial Strategies edited by Christopher Morton and Darren Newbury London: Bloomsbury, 2015. 245 pages, 72 b/w ill., bibliography, index. $112, cloth.

<b>The African Photographic Archive: Research and Curatorial Strategies</b> edited by Christopher Morton and Darren Newbury London: Bloomsbury, 2015. 245 pages, 72 b/w ill., bibliography, index. $112, cloth.

DNA quantification of basidiomycetous fungi during storage of logging residues.

The demand for bioenergy caused an increased use of logging residues, branches and treetops that were previously left on the ground after harvesting. Residues are stored outdoors in piles and it is unclear to what extent fungi transform this material. Our objective was to quantify the amount of wood degrading fungi during storage using quantitative real-time PCR (qPCR) to detect basidiomycetous DNA in logging residues, a novel approach in this field. We found that the qPCR method was accurate in quantifying the fungal DNA during storage. As the moisture content of the piled logging residues decreased during the storage period, the fungal DNA content also decreased. Scots pine residues contained more fungal DNA than residues from Norway spruce. Loose piles had generally more fungal DNA than bundled ones.

Recovery of Oplopanax horridus (Sm.) Miq., an Important Ethnobotanical Resource, after Clearcut Logging in Northwestern British Columbia

Normal 0 false false false MicrosoftInternetExplorer4 The persistence and recovery of devil’s club ( Oplopanax horridus (Sm.) Miq., Araliaceae) after clearcut logging in northwestern British Columbia, Canada, is investigated through a series of retrospective surveys. This species remains important to the traditional culture of many First Peoples of western North America and is being studied for its biological abilities by medical researchers. Based on observations in 16 clearcuts that had been logged 3 to 37 years earlier, it is clear that devil’s club can survive and grow in these disturbed habitats and appears to take at least 10 years for sizes to recover to those found in old-growth forests. The most successful populations of post-logging devil’s club probably escaped damage during logging operations, showed no recent signs of fire, and were associated with loose piles of dead branches, tree tops, and rotten logs. Consideration of these factors in forest management, in combination with the time since logging, should facilitate the resilience and sustainability of this species. /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;}

Modeling gravitational collapse of rectangular granular piles in air and water

The present paper is concerned with the two-dimensional collapse of piles of granular materials, a problem analogous to the classical dam break problem in hydraulics. This study is intended to aid in the development of constitutive equations and modeling procedures that can be applied to predict various flows involving high concentration liquid–particle mixtures. We consider the granular collapse as a test problem and attempt to validate our modeling by comparing our predictions with previously published granular collapse experiments. The time-dependent evolution of the collapsing granular piles is calculated by making use of COMSOL, a commercial finite element code that is designed to handle a wide variety of Multiphysics problems. We begin by considering the collapse of a rectangular block of dry granular material and calculate the temporal evolution of the free surface by making use of the Level Set method. Good agreement is found between these predictions and the laboratory experiments of Balmforth and Kerswell (2005). The collapse of granular material submerged in a water is then investigated using a Mixture Model approach. The experiments of Rondon et al. (2011) revealed drastically different collapse periods depending upon whether the initial pile was in a loose or a dense, compacted state. The simple Mixture Model approach gave reasonably good predictions of the Rondon et al. (2011) experiments for the case of initially loose piles that collapsed in about a second, but it was unsuccessful in simulating the collapse of the initially dense piles that were observed by Rondon et al. (2011) to take around 30–40s. Some simple empirical modifications to the material constitutive behavior were able to roughly predict such long collapse times, but a more comprehensive and detailed investigation of the phenomenon is warranted.

First record of ambrosia beetle (Euplatypus parallelus) infestation on cashew from Goa, India

The occurrence of ambrosia beetle Euplatypus parallelus (Fabricius) (Coleoptera: Curculioninae: Platypodinae) infestation on cashew (Anacardium occidentale L.) is reported for the first time from Goa, India. Most of the infested trees were either previously attacked by cashew stem and root borer Plocaederus ferrugineus (Coleoptera: Cerambycidae) or were pruned trees. The visible symptoms of attack include appearance of numerous round bore holes on the tree trunk and branches, and extrusion of fibrous dust frass on the tree trunk and in loose piles at the base of the tree. Large numbers of larvae, pupae and adults were observed in the galleries of the affected trees. Adult beetles measure 4.0–4.3 mm in length and are brown in color, having long and slender bodies with yellow hairs. They have a characteristic feature of absence of pores on the pronotum. Male and female insects were identified based on the elytral declivity.

Nearing Sligo, and: Hy-Brazil, and: Inside Outside

Nearing Sligo, and: Hy-Brazil, and: Inside Outside Sandra Bunting (bio) Nearing Sligo Closed in behind grey stone walls,checkerboards of sheep and crowsspread out on either side of the road:crows no worse than sheep. Last traces of November leavesform faded yellow arches,scatter in the wind and drop,loose piles in wet russet ditches. I was not ready for Ben Bulbenor the poet's Isle of Inishfree,the contours of Lough Gil windingan enchantment suddenly upon me. Quite the opposite to a nightmare,soft noises of crows and sheep in sleep:the existence of something goodyou can't see yet know is there. [End Page 12] Hy-Brazil The island glittersin the middle of the ocean,an arcane citybuilt on a living formsubmerged at the deepestpart of the Atlantic,a green star flickering,only to vanish and reappearsomewhere else. I have seenits other side—the dark side.It moves along the ocean bed,occasionallycoming up for air. When you are pregnant,so is every other womanyou see, or so it seems.When someone you loveis afflicted, you see paineverywhere. Hy-Brazil is an island in Irish mythology that appears and disappears. [End Page 13] Inside Outside We are passing clouds that watchtime churn up Galway flotsam,little pearls scooped in an oyster shell,scattered within walls to find a place,always selecting, shaping our stories. Time scrapes the muddy bottomof the river where our thoughts form.Everything changes and remains the same.In from the bay voices blow. Windowpanes dissolve like barley sugar in the rain. Ghosts whisper messages from the past.Our footsteps, heavy on smooth stone,reach out for pebbles from a common pool.Time shifts again, comes togetherto let the light in; we have let in the light. Sandra Bunting Sandra Bunting is presently working as an editor for Gaelóg Press and is on the editorial board of Crannóg magazine. She previously worked at the National University of Ireland-Galway at the Academic Writing Centre and facilitated creative writing seminars there. Copyright © 2011 University of Nebraska Press

Tsunami-generated boulder ridges in Lake Tahoe, California-Nevada

An array of east-trending ridges 1-2 m high and up to 2 km long occurs on the Tahoe City shelf, a submerged wave-cut bench <15 m deep in the northwest sector of the lake. The shelf is just north of the amphitheater of the giant subaqueous 10 km 3 McKinney Bay landslide, which originated on the west wall of Lake Tahoe. Images from a submersible camera show that the ridges are composed of loose piles of boulders and cobbles that lie directly on poorly consolidated, fine-bedded lake beds deposited in an ancestral Lake Tahoe. Dredge hauls from landslide distal blocks, as well as from the walls of the reentrant of the landslide, recovered similar lake sediments. The McKinney Bay landslide generated strong currents, which rearranged previous glacial-derived debris into giant ripples creating the boulder ridges. The uncollapsed part of the sediment bench, including the Tahoe City shelf, poses a hazard because it may fail again, producing a landslide and damaging waves.

The Vulture Tree

The Vulture Tree Katie Fallon (bio) To be eaten by that beak and become part of him, to share those wings and those eyes— What a sublime end of one's body, what an enskyment; what a life after death. Robinson Jeffers, "Vulture" The tree's bleached branches twist like misshapen arms, skeletal and bowed as they reach towards the cloud cover. It stands stark along Interstate 79 as I drive past; behind it billows a green curtain of leaves and pastures. Vultures hunch in crooks of the tree's elbows, talons wrapped around knots in the dead wood. There isn't an official term for a group of vultures, and flock seems too gentle—I call them a hunch of vultures. Hunch describes them best. They hunch together in the tree, they even seem to hunch when they soar. The vultures scan the highway as a light rain begins to fall. One spreads its wings. Another shivers and shakes drops from its feathers. Perched like black gargoyles they hunch and wait for something to die. I turn off the interstate and pull into the West Virginia Raptor Rehabilitation Center. My husband, Jesse, has already arrived; his silver car parked between poplar trees in the gravel driveway. Earlier the center received a call about an injured turkey vulture. It had been limping around on the ground behind a shopping center, trying to hide amid dumpsters and piles of scrap metal. An army of feral cats had kept their distance, but hissed and growled when the bird dragged itself from one filthy crevice to another. Jesse rescued the bird and transported it here for treatment. Inside the raptor center, Jesse has already begun to examine our patient. The vulture is weak. Jesse wraps his hands around the bird's emaciated body; its red head droops as it tries to struggle out of his grasp. The feathers of the vulture's underside are matted with dried feces; it must have been on [End Page 113] the ground for days. We weigh the bird, shine a flashlight in its brown eyes, and gently stretch each wing. Besides being very thin it has no obvious injuries. We put the vulture in an ICU cage, and I split the belly of a deadrat and slide it toward the bird. It tears the rodent from me with its beak, turns its back to us and silently strips the meat from the rat's bones. A vulture is primal. It lives by the deaths of other creatures, but it's not a predator. A hawk, for example, hunts—stalks, stoops, and squeezes the life from its prey, rips through bodies with razor talons. A turkey vulture waits. It isn't a murderer, and it doesn't kill, but it's impossible not to think about death with a vulture nearby. Through the steel cage bars, I watch the starved bird devour its meal, skinning meat and sinew from wet bones. It turns the rat almost inside out, holds a corner of pelt under a toenail and skillfully cleans the hide. The end of this bird's beak is curved like a crochet hook, a delicate tool for knitting through organs, separating muscle from bone, from skin. The vulture is an intricate and meticulous artist. In a few minutes the rat is empty. Its skin folds like baggy pants in a loose pile around its large thigh bones. The bird seems satisfied and drags what remains of the rat to a back corner of the cage to save for later. It looks over its hunched shoulder at me, cautiously turns, and steps onto a rope-wrapped perch. We don't treat many turkey vultures at the raptor center. I would like to believe that their intelligence allows them to avoid moving cars and humans; it seems more likely though that people have greater respect and pity for injured hawks and eagles. Eagles are symbols of nations; we see them as majestic birds to be proud of, and we put their likeness on currency and leather jackets. Vultures have become greedy, sneaky undertakers. I think injured vultures might be left to die. A few weeks ago Jesse and I...

The Effect of Delayed Ensiling and Application of a Propionic Acid-Based Additive on the Fermentation of Barley Silage1,2

Prolonged exposure to air can adversely affect the silage fermentation process. To investigate a possible method to overcome this problem, we determined if a buffered propionic acid-based additive, applied to chopped, whole-plant barley exposed to air before ensiling, would affect the subsequent fermentation. Wilted forage was chopped and treated with nothing, or with 0.1% (wt/wt wet forage) of a buffered propionic acid-based additive and ensiled immediately in quadruplicate 20-L laboratory silos. Portions of the chopped forage, untreated and treated, were left in loose piles in a barn for 24h before ensiling. Another portion of the untreated silage exposed to air for 24h was also treated with 0.1% of the additive just before ensiling. Prolonged exposure to air before ensiling increased the numbers of yeasts on forages by more than 1000-fold. The concentrations of water-soluble carbohydrates decreased by more than 50%; the ammonia-N concentrations increased 40%, and pH increased by more than 1 unit as a result of exposure to air. These changes were less in forage that was treated with the additive at chopping. After 60 d, silages of forages that were exposed to air before ensiling had a higher pH, higher concentrations of ammonia-N and butyric acid, and lower concentrations of lactic and acetic acids than silages of forage that had been ensiled immediately after harvest. In situ DM digestibility was lowest in untreated silages that had been exposed to air before ensiling. In contrast, treatment with the additive, applied before or after exposure to air, prevented the reduction in in vitro digestion.

The use of alarm pheromones to enhance bait harvest by grass-cutting ants

The enhancement of bait for the control of grass-cutting ants was investigated using two species of grass-cutting ant, Atta bisphaerica (Forel) and Atta capiguara (Gonçalves) (Hymenoptera: Formicidae). Bait was applied in loose piles to obtain a direct relationship between ant attraction and bait harvest. Enhancement with alarm pheromone compounds significantly increased the attractiveness and harvest of bait under certain conditions. A large proportion of the ants attracted to the enhanced bait were minor workers. These ants rarely transport bait because of their small size, and so it may be possible to increase the effect of bait enhancement by using smaller bait granules. Foragers of A. capiguara were less inclined to transport citrus-pulp bait than were those of Atta laevigata (Fr. Smith), a species that also harvests dicotyledonous plants. This emphasizes the importance of developing a bait matrix that is more acceptable to grass-cutting species. Nevertheless, the results suggest that alarm pheromone compounds have significant potential to improve the efficacy of baits for the control of grass-cutting ants.

The porosities of ordinary chondrites: Models and interpretation

Abstract— Densities and porosities for 285 ordinary chondrites have been assembled and analyzed. Measured chondrite porosities are bimodal; finds have an average porosity of &lt;3%, whereas fall porosities average 7% but range from zero to &gt;30%. We conclude that mild degrees of weathering fill pore spaces, lowering grain densities and porosities without significantly changing the bulk size or mass of the sample. By assuming an original pristine grain density (as a function of the meteorite's mineralogy—determined by its class), we can derive model pristine porosities. These model porosities cluster around an average value of 10% for all classes of ordinary chondrites.Ordinary chondrites do not show any correlation of porosity (model or measured) with petrographic grade or sample size (over a range from 0.2 g to 2 kg). However, we do see a correlation between shock state and porosity. Shock‐blackened meteorites are less porous than other meteorites. Furthermore, less severely shocked meteorites show a much broader range of porosities, with the maximum porosity seen among meteorites of a given shock class falling linearly as a function of that shock class. This is consistent with the idea that shock compresses and closes pore space.Analysis of meteorite porosity provides a lower bound to the fine‐scale porosity of asteroids. Our densities, even with 10% primordial porosity, are significantly higher than inferred densities of possible asteroid parent bodies. These asteroids are probably loose piles of rubble.

The Effects of the Chelating Agent Ethylenediamine Tetra-acetic Acid on Cell Adhesion in the Slime Mould Dictyostelium discoideum

ABSTRACT Vegetative myxamoebae and pseudoplasmodia of the slime mould Dictyostelium discoideum were treated with the chelating agent ethylenediamine tetra-acetic acid. The myxamoebae first respond by rounding up, and then by throwing out active, continuously moving, hyaline lobopodia. At high concentrations of EDTA the cells are unable to migrate, although cellular ‘writhing’ continues for hours. At lower concentrations writhing also occurs, but the cells are able to move together into loose heaps. A migratory pseudoplasmodium immersed in 5 mM EDTA begins disaggregating rapidly. Its smooth surface breaks down and individual cells exhibit membrane activity similar to that described above. The cells lose their attachments to one another, and are maintained in a loose pile only by a tenuous matrix in which they appear to be embedded. Mild agitation now easily separates them into single cells and small clumps of cells. The effects noted on both myxamoebae and pseudoplasmodia are reversible by replacing the EDTA with Bonner’s solution. Moreover, preparations treated with EDTA in the presence of equimolar concentrations of calcium chloride are unaffected. How the removal of cations from cells might result in their dissociation from one another is discussed. It is suggested that EDTA may have its effects by (a) dissolving extra-cellular ground substance or sheath material, and (b) producing a state of instability in the cell membrane allowing continuous pseudopodia! activity and distortion of relations between apposed cell surfaces.

Expanding Horizons in the Recognition of a Phylum

The field of systematics has often been ridiculed, especially by biologists engaged in other aspects of science. Occasionally the writings of some systematists have merited this lack of respect but this fact provides neither reason nor excuse for belittling the entire field. The chief cause for contempt of systematics has been a lack of appreciation on the part of other biologists for the methods and objectives of taxonomic work. There has been a wide spread but fallacious belief that physical and chemical phenomena are objective realities while species and other taxonomic concepts are purely subjective creations of the human imagination. The apparent disregard for taxonomy has some times been voiced in the figure which rates the taxonomists as the hod-carriers of science. Those who hold such derogatory attitude toward the objectives of the taxonomist seem to have forgotten that the mortar carried by the hod-carrier is the stuff which gives stability to the wall. Without cooperation of hod carriers, the walls of biology would be but a loose pile of toppling bricks or stones, lacking pattern and orderliness. However, if the taxonomist is rated as but a menial laborer whose function is that of carrying the cohesive mortar for the edifice of biology, how much lower in the social scale of scientific castes must be the student of nomenclature who inspects the bricks for conformity and rejects those with flaws before they weaken the wall. All too often faulty material escapes first inspection and then part of the structure must be torn down so that the defective units may be replaced. To carry the figure a bit farther; we might say that the student of nomenclature is the apprentice to the hod-carrier since it is he who moistens the sand of personal endeavor and the lime of public opinion with the water of common sense and precedent to form the mortar for binding together the units constituting the structure of taxonomy. Instead of attempting to organize a brief in defense of the fields and practices of taxonomy and nomenclature, this address will be devoted to tracing the growth of information regarding a single phylum, the Acanthocephala, or thorny-headed worms. In its history this group provides excellent material to illustrate the steps in the gradual expansion and evaluation of concepts in taxonomy. In the earliest days before the status of this group was understood, species now regarded as belonging within it were promiscuously assigned to various genera now recognized as representing several distinct phyla. By easy stages the knowledge of detailed