Prof essor of Zoology in Yale rnirersity arid KATHARINE J. BUSH, in Pcabody Museum of Tale I'nicersify.THIS article is not intended as a review of all the known species found oft' our coasts. It is preliminary to a much more extensive report, in which full details of the distribution of all the species collected will be given, and for which the detailed tables have been prepared, giving every station for each species, with its position, depth, temperature, character of the bottom, etc.Many of the larger and more prominent species were described and figured by the senior author several years ago in various papers published in the Transactions of the Connecticut Academy and elsewhere.Tlie smaller and more difficult species were put aside at that time, for more careful study, and are now presented.The families that are most fully treated in this article are the Lediclae, Cuspidaridpe, Diplodoutida-, and Pectiimhe. These include a very large number of deep-sea species in every region, and their species are often very difficult to distinguish without long and patient microscopic study and direct comparison of large series of specimens from various localities.The present article is intended to give some of the results of studies of this kind, made during several years, of the large series of speci-'Owing to the long delay iu the publication of this article, some of the new species and genera have been published elsewhere, so that these numbers are not now strictly correct. NO. H39. nr.KP-WATEi; Moi.i.rst'A VKRHILL AXI> r.rsii. 777 Family PHOLADIIKE. MARTESIELLA, new subgenus. This subgeneric name is proposed for the following species, which ditt'cis from Narlcsia in having a well-delined, elongated, median, dorsal plate, posterior to the umbos, in addition to the shield-shaped one over them. MARTESIA (MARTESIELLA) FRAGILIS, new species. (Plate LXXIX, liy. ID. i Shell small, white, thin, fragile, wedge-shaped. The anterior end is very short and broadly rounded, the aperture nearly closed in our largest specimen by a pair of callous plates. The anteio dorsal margin is recurved toward the uinbos, but not appressed, and forms a deep, spiral, open cavity. The valves have a very obtuse anterior emargiuation.A broad and moderately deep sulcus runs from the beak to the ventral margin; in front of this the surface is covered by thin concentric ribs, which curve down waul at the sulcus and form a distinct angle in line with the anterior emargination and corresponding with a slight ridge on the surface; these concentric ribs are crossed by tine radiating lines, which produce tine serrations on their edges. Posterior to the sulcus the surface is marked only by irregular lines of growth, which, near it, take the form of more distinct grooves or ridges. The posterior end is prolonged, compressed, and bluntly rounded. The umbonal plate is thick, relatively large, and usually heart-shaped, with the posterior end broader and distinctly emarginate in the middle; the anterior end tapers somewhat and is blunt and angulated, or sometimes s...
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