o. 1139. DEEP-WATER MOLLUSCAVERRILL AND BUSS. 875 



rower; its groove is narrow and inconspicuous. The hinge-margin 

 itself is rather thin and bears very numerous, erect, V-shaped, acute 

 teeth which number, in the large specimens, about sixteen or seventeen 

 in the anterior series and about thirty-two or thirty-three in the poste- 

 rior, including a number of small proximal ones; beneath the beaks 

 there is a smooth, edentulous space, often a little thickened at the inner 

 margin and projecting a little inward in the middle, and continuing 

 inside the series of small proximal teeth on each side. In some cases 

 this thickened border seems to arise anteriorly and to pass under 

 the posterior series, as a slight fold; in other cases it is continued 

 directly from one series to the other. The posterior series is nearly 

 straight and about twice as long as the anterior which is strongly 

 curved and distally somewhat recedes from the thin dorsal margin. 

 The anterior end of the shell is rather short and evenly rounded; the 

 posterior is about twice as long, a little wider owing to a slight ventral 

 expansion, compressed and obtusely rounded or subtruncated at the 

 margin, but without any distinct carination or angulation. The pallia! 

 sinus is very broad and deep, extending nearly to the middle of the 

 shell. The inner surface is smooth, white or grayish white. The 

 exterior is smooth, except for the delicate lines of growth, and covered 

 with a thin, brilliantly iridescent epidermis which, in live specimens, 

 is pale yellowish green, but in dead valves is pale straw color. 



Our larger specimens measure about 15 or 1C inm. in length and 9 or 

 9.5 mm. in height. 



Found at many stations between N. lat. 41 28', W. long. 65 35', and 

 K lat. 35 16', W. long. 75 2' 30", in r>lG to 1,781 fathoms, 1883-1887. 



MALLETIA ABYSSORUM, new species. 

 (Plate XC VII, tig. 7.) 



Shell small, not much compressed, lustrous, iridescent, subovate, not 

 gaping, decidedly inequilateral, with the posterior end the longer, 

 broader, obtusely rounded, without any distinct rostration. Ulnbos 

 rather prominent, rising above the outline of the dorsal margin, with 

 small beaks turned backward at the tip. Lunule and escutcheon abor- 

 tive. The short antero-dorsal margin is slightly concave, and slopes 

 rapidly to the slightly angulated anterior end; the ventral margin is 

 very broadly and evenly convex, the curvature receding somewhat pos- 

 teriorly, so that the greatest height of the shell is somewhat back of the 

 middle, posteriorly there is a slight extension of the edge correspond- 

 ing to an indistinct radial ridge; the posterior end is very broad, 

 obtuse, not angulated, with the dorsal margin nearly horizontal, slightly 

 convex, compressed and forming a slight angle where it joins the poste- 

 rior curve. A very slight groove defines a very faint escutcheon, along 

 the edge of which the teeth can be seen through the substance of the 

 shell. The surface is polished, brilliantly iridescent, and is marked by 

 faint, raised, concentric lines, or ridges parallel with the lines of growth 5 



