NO. 1139. DEEP-WATER MOLLUSCAVEEEILL AND BUSH. 867 



Our specimens, which are worn and imperfect, referred to this north- 

 ern species, differ somewhat from the typical specimens from Spitz- 

 bergeu, received from Doctor Friele. They are relatively shorter, 

 higher, and somewhat less swollen, with a thicker and heavier shell. 

 The posterior end is less produced and less tapered, so that it has a 

 more ovate form. The hinge-teeth are stouter; the posterior series is 

 shorter but contains the same number of teeth in specimens of similar 

 size. With the amount of material that we have for examination, the 

 differences, however, seem hardly sufficient to warrant the separation 

 of our shells as a distinct species. We therefore propose the varietal 

 name unthlia for our specimens. 



A few separate valves, at two stations, north of Cape Cod, in 110 to 

 1131* fathoms, 1878-79. 



YOLDIELLA FRATERNA, new species. 

 (Plates LXXX, fig. 5; LXXXII, fig. 8.) 



Toldia friyida VEKRILL, Trans. Conn. Acad., VI, p. 279, 1884; Expl. Albatross, 

 Eeport U. S. Com. Fish and Fisheries for 1883, p. 576, 1885 (in part). 



Shell small, thin, delicate, irregularly elliptical in form, the posterior 

 end being a little the longer, unusually broad, and slightly produced 

 above, but not distinctly augulated. with a glossy, iridescent, yellow- 

 ish green epidermis. Umbos a little swollen ; the beaks small, scarcely 

 prominent, and subcentral. The anterior end is broad, a little produced 

 in the middle, and obtusely rounded; the dorsal margin is nearly 

 horizontal in the region of the teeth; distally, sharp, and convex, then 

 sloping rapidly to the middle of the anterior end. The ventral margin 

 is broadly rounded, expanding a little posteriorly and then ascending 

 pretty rapidly to the posterior tip which is obtusely rounded superi- 

 orly; postero-dorsal margin slightly convex and nearly horizontal for 

 the greater part of its length. The surface beneath the epidermis is 

 marked only by faint lines of growth. The hinge-margin is thin, 

 rather delicate, with the two series of teeth of nearly equal length and 

 diverging from the beaks at a broad angle; each series contains about 

 ten rather thin and delicate teeth, of which the one or two proximal 

 ones are very small and rather indistinct. Beneath the beak the 

 margin is attenuated and interrupted by a small, oblong resilium which 

 occupies the entire thickness of the margin and a slight notch in the 

 beak. The pallial sinus is relatively rather large and deep, but in 

 most specimens is invisible. 



Length of the figured .specimen, 4 mm.; height, about 2 mm. 



A comparatively small number of specimens, at about twenty sta- 

 tions, between N. lat, 47 40', W. long. 47 35' 30", and N. lat. 37 8', 

 W. long. 74 33', in 90 to 1,608 fathoms, 1873-1886. 



This is a deep-water form formerly identified by us as Yoltlia friyida 

 Torell. 



