No description available.

review of Red Crag literature places this study in context with work on Crag Geology. Results from recent work on the Icenian Crag differ markedly from those of earlier workers, and this study is an attempt to re-examine the Red Crag in the light of these recent results. The limitations of Harmer's methods are discussed. Quantitative methods for studying Red Crag Mollusca are described, ~d assemblage-types are recognised. Information about the molluscs (Appendix II) is used to subdivide assemblages into ecological groups, which are used for palaeoecological interpretations. The relationship between certain extinct species and extant species is studied. Sedimentary structures and granulometric analyses are important in assisting the palaeoecologic interpretations.

No description available.

A study of the British members of the family Grammysiidae S.A Miller 1877 has been undertaken. Most of the taxa are Silurian in age; others are, rarely, Upper Ordovician or Devonian in origin. One species found derived in Triassic strata is included and its origin traced. Wherever possible, existing type material has been located and a primary revision made. This work has been augmented by studies on new and existing collections. The diagnosis of the family has nov been restricted to include only those members of the Superfamily Pholadomyacea vhich show the characteristic Grammysiid cincture (fold and/or ribs) crossing the shell from the umbo to the ventral margin to there cause a folding of the shell. The type genus Grammysia De Verneuil 1847 is redescribed; its type species and type specimen designated and described. Numerical taxonomy has been used extensively and each species' description is accompanied by a table(s) of measurements. Three new genera and several new species are described. One chapter is devoted to computer applications in the study of Grammysiid bivalve systernatics, evolution and ontogeny. It includes sections on cluster analysis and discriminant analysis and evaluates the uses of these techniques in the various branches of 'palaeontology'. The section on palaeoecology gives a detailed discussion of the mode of life end habitat of each of the 19 species described in the section on systematic palaeontology. It discusses the functional significauce of the Grammysiid cincture and illustrates the Grammysiidae in their life positions and habitats at several periods from Ashgillian to Devonian times. The importance of environment to evolution is discussed. A summary of the evolution of the Grammysiidae is included. A new technique for coating fossils prior to photography is described.

No description available.

No description available.

No description available.

The investigations reported in this thesis have been carried out primarily on British representatives of the Archaeogastropoda. The work falls into two parts the first relates to the fine structure of epithelial sensory cells and the second to the fine structure and function of the juxtaganglionar organ, a putative endocrine gland. Observations on the sensory cells are primarily concerned with those found in the cephalic and epipodial tentacles, and the epipodial sense organs. The general organisation and innervation of these structures is described together with the ultrastructure of their sensory cells. The species examined most extensively were Gibbula umbilicalis (da Costa) and Emarginula reticulata Sowerby. Much similarity was observed between these species, particularly with regard to the epipodial sense organs. Similar structures were also found on the mantle edge bordering the shell slit of E. reticulata. Members of the Patellacea were examined briefly for comparison. Fine structural observations on the juxtaganglionar organ were carried out on G. umbilicalis. The organ was found to possess many features characteristic of an endocrine gland and to show similarity to the dorsal bodies of pulmonates. Animals were collected at monthly intervals throughout one year in order to investigate the possibility of seasonal variation in the activity of the organ. Such variation was observed in females and was shown to correlate with the reproductive cycle. Males were not examined in this respect. The juxtaganglionar organ of an opisthobranch, Aplysia punctata Cuvier, was examined for comparison. It was found to exhibit further similarity to the pulmonate dorsal bodies.

Flora S. Tsai. / Includes bibliographical references (leaves 48-49). / Research supported by the National Science Foundation. ECS 90-16437 Research supported by the Naval Research Laboratory. N00014-90-K-2018

No description available.