1894. 



PROCEEDINGS OF THE NATIONAL MUSEUM. 689 



twisted; in the young shell a prominent thread radiates from the beak, 

 setting off a i^osterior area over whieh the grannies do not have a dis- 

 tinct linear arrangement, but as the shell grows this thread becomes 

 obsolete, though the difference in the distribution of the grannies con- 

 tinues; internal surface of the valves polished, pearly, with obscure 

 radiating and some vermicular imi:)ressions, the internal margin of the 

 valves liuely grooved radially; nmscular impressions sunill, somewhat 

 obscnre, the posterior larger; external ligament thin, short, hardly 

 functional; internal resilium short, strong, set obliquely under the dor- 

 sal margin and reenforced below by a calcareous lithodesma, thick, delti- 

 form, rounded below with a short, pointed process on each side behind; 

 there is a small, nearly smooth, deeply imi)ressed lunnle mostly attached 

 to the right valve, the margin here projecting, while in the left valve 

 a similar projection is so depressed as to pass for the most part below 

 the projection of the right valve and perform the function of an anterior 

 lateral tooth; the left valve behind the beak shows a long, almost linear, 

 depression, which must be taken as the escutcheon, the most i)osterior 

 l)art of which passes below the margin of the right valve, while on the 

 e{\gQ of the latter, close to the resilium, is a small, little-elevated, nar- 

 row lateral tooth; in front of the resilium in the right valve is a large, 

 stout, pointed, recurved cardinal tooth arising from the valve under the- 

 Innnle and hooking into a funicular cavity below the beak of the left 

 valve. Behind this in the left valve is a narrow little elevated cardinal, 

 easily mistaken for a raised edge of the cartilage pit, and serving to 

 defend the lithodesma from pressure by the right cardinal. Using c for 

 the cartilage and I for the lateral teeth, the Steinmann formula for the 



hinge wonld be as foUows: t>— 7 ,^, •■, though the laterals do not enter 



' 3\ V CO 1 



actual sockets in the opposite valve. Ueight of the shell, 25; length, 

 28 ; diameter, 21 mm. A dead valve reaches a length of 38 and a height 

 of 35 mm. 



Stations 3471, 3472, 3474, 3475, and 3476 in 295 to 375 fathoms; tem- 

 perature between 43° and 44° F. Nos. 107008, 107027, 107028, 107029, 

 107030, and 107031, U.S.N.M. 



This tine species differs from E. eburnea by its recnrved, smaller, and 

 more delicate and more numerous granules. It is more like E. elef/ant- 

 issiiiia, from which it differs in the rounder form of the young shell 

 and in the full grower by its thinner and anteriorly more produced 

 valves. The minor details of the hinge, and the position of the pallial 

 and muscular impressions on the valve also serve, when carefully com- 

 pared, to discriminate the species. 



The soft parts offer several i)oints of interest already alluded to. 

 The tissne, internal to the mantle and external to the viscera, espe- 

 cially on the ventral surface, is remarkably thick, almost jelly- like, 

 and full of connective fibers. The margin of the mantle appears 

 smooth and somewhat thickened by peripheral muscular fibers form- 

 Proc. N. M. 94 44 



