. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 280 Bulletin Museum of Comparative Zoology, Vol. 145, No. 6 Table IV. Records for Silicula mcalesteri NEW SPECIES. Cruise No. Sta. Depth (m) Speci- mens Latitude Longitude Gear Date Atlantis II 60 280 275- 305 ARGENTINE BASIN 39 36°'S- 36°'S 53°'W ES D. 1—r L ENGTH (mm) Figure 17. Size/frequency distribution of specimens of Silicula fragilis collected from Stations 126 and 85 and sorted according to sex and gonadial development. dorsal margin behind the umbo convex in front of t
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 280 Bulletin Museum of Comparative Zoology, Vol. 145, No. 6 Table IV. Records for Silicula mcalesteri NEW SPECIES. Cruise No. Sta. Depth (m) Speci- mens Latitude Longitude Gear Date Atlantis II 60 280 275- 305 ARGENTINE BASIN 39 36°'S- 36°'S 53°'W ES D. 1—r L ENGTH (mm) Figure 17. Size/frequency distribution of specimens of Silicula fragilis collected from Stations 126 and 85 and sorted according to sex and gonadial development. dorsal margin behind the umbo convex in front of the umbo, slanting abruptly down- wards to the anterior limit of the shell, such that the dorsal and ventral margins merge in a smooth curve; shell margin, immedi- ately anterior and posterior to the umbo forming small concavities; posterior margin narrowly truncate; anterior margin sharply and evenly rounded; ventral margin long and gently curving; shell gaping anteri- orly and posteriorly, the valves separated along part of the dorsal margin (Figs. 5, 18). Hinge plate long, thin, and weak; pos- terior hinge plate long, straight, and paral- leling the dorsal shell margin; anterior hinge plate short, straight and angled ventro-an- teriorly. Opisthodetic ligament large, elon- gate, originating below the umbo and directed transversely in a ventroposterior direction. Posterior hinge plate with 6-8 very narrow, elongate teeth, only the largest specimens having 7 and 8 teeth; the most proximal tooth small, being readily over- looked, and rising from the thickened hinge plate immediately behind the umbo and above the ligament; the second tooth is also small, but three times the length of the first, and positioned on the hinge plate immedi- ately below and behind the first, above the distal end of the ligament, and slanting pos- teriorly and dorsally away from the hinge line towards the dorsal margin; remaining teeth considerably longer, and continu- ously overlapping, on hinge li
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