N...n:!9. />/?/:/- (r. r/7-; /,- voLLUSCArERRiLL .ixi> /.T.V//. 843 



loi(l<'n (Sracchi) audits varieties, grandisVerrillj FreHei Jeffreys, MylcH- 

 trioHnli* Sars, <-rc>tnl<tt<i Verrill, <-hi<-!tl1 Dall, from off St. Vincent, 

 northward. />'. f/ldcidliti (dray), Arctic America and Europe. />'. <ino- 

 ><il<( Verrill and Bush, Gulf of Maine. />'. ((In/Nxontm Verrill and Bush, 

 off I >ela\vare Bay. 1>. }-j'ini<li<-<>l<i Verrill, from off West Indies, north 

 ward, />. (/loiitrriilft (Dall), 11. polyci/nia (Dall), B. culebrcnsis (Smith), 

 off West Indies. />'. iiucijitixcitlpla (Smith), B. plo-ocxwi (Smith), Atlantic 

 and Pacific. B. inntata (Smith), Pacific. 



r>c)ii]i(u-ca ((Ni'>-nla (Dall), and B. aayrhmta (Dall), are from the West 

 Indies, in deep water. 



BATHYARCA ABYSSORUM, new species. 

 (Plate LXXVI, %. It. . 



Shell small, short, well-rounded at both ends, swollen, inequilateral, 

 slightly oblique, with a rather long 1 , straight hinge-margin. Tmbos 

 large, swollen, prominent. Beaks prominent and curved strongly for- 

 ward, situated considerably in front of the middle. Surface every- 

 where covered with nearly equal, delicate, raised, radiating lines and 

 small, rather even, raised lines of growth; these together produce a 

 finely cancellated surface which, when fresh, is covered with a thin 

 brownish-yellow epidermis forming small scale-like points at the inter- 

 section of the lines; the surface is also marked with slight, irregular, 

 concentric waves or undulations. 



The anterior margin is shorter than the posterior and forms an 

 obtuse, rounded angle at its junction with the hinge-margin; the ven- 

 tral margin is obliquely curved, most prominent behind the middle, 

 where the curve forms nearly the segment of a circle; posterior margin 

 is very broadly rounded and forms a distinct obtuse angle where it 

 joins the dorsal margin. The ligamental area is lanceolate, mod- 

 erately large, decidedly wider just in front of the beaks, becoming nar- 

 row and pointed posteriorly. The dark ligamental patch is arrow- 

 shaped, situated behind the beaks. The hinge margin is rather wide 

 and strong, with a small, central edentulous space, mostly behind the 

 beaks. The teeth, which are striated on the sides and creuulated on 

 the edge, are equally and decidedly oblique in the two series; the prox- 

 imal ones are small and the others increase in size and obliquity to 

 near the end of the series, where one or two of the outermost are 

 decidedly smaller and very oblique. In the largest specimen there are 

 about six teeth in the anterior and eight in the posterior series. The 

 inner surface shows faint radial grooves and ridges, much coarser than 

 the external striie; there is also a fine, impressed line, with a finely 

 creuulated edge close to the margin. 



Length of the largest specimen, mm.; height, G.5 mm.; thickness, 

 5.5 mm.; length of the hinge margin, 3.5 mm. 



Three specimens were found at stations 2713 and 1'714, off Delaware 

 Bay, in 1,825 to 1,859 fathoms, 1886. 



