K. J. Bash — Molliiscii of (Jape Haftenis. 473 



the dorsal margin is convex, and falls off" abruptly to the obtusely 

 rounded anterior end. The ventral margin is broadly rounded and 

 projects outward in an acute angle, at the pi'ojection of each of 

 the principal ribs; the intervals between these angles are usually 

 concave, and beyond the last rib the outline recedes in a concave 

 curve to the origin of the rostrum, which is rapidly narrowed to near 

 the tip. Of the three principal radiating ribs, the middle one runs 

 from the beak nearly to the middle of the ventral margin, curving a 

 little backward; the posterior one terminates about midway between 

 the former and the end of the rostrum, curving strongly backward ; 

 the most anterior one ends about midway between the middle one 

 and the anterior end of the shell ; midway between this and the mid- 

 dle one, there is a smaller secondary rib. These three primary ribs 

 are strongly elevated, not very broad, with the summits rather thin, 

 finely notched by the concentric lines of growth ; the most posterior 

 one is the largest and highest, and projects the most at the margin. 

 Between these ribs the spaces are wide and strongly concave, marked 

 by numerous and regular lines of growth. On the anterior end of 

 the shell there are two or three smaller radiating ribs, which are sep- 

 arated by intervals about equal to their own breadth, and give the 

 margin a slightly crenulated appearance. The rostrum is narrow, 

 strongly compressed, with both the dorsal and ventral outline con- 

 cave. Two small ridges run from the beak to the tip of the rostrum, 

 separated by a very narrow, flattened area. The right valve has two 

 well-marked latei'al teeth, the posterior one considerably longer and 

 larger than the anterior ; between these there is a small, ovate cartilage 

 pit. The inner surface of the valves shows deeply indented grooves 

 corresponding to the primary external ribs. Color, opaque white. 

 Epidermis indistinct. 



Length of the largest specimen, 6'"™ ; height, 4™'" ; thickness, 4'"™. 



Four living and two dead specimens were found at stations 2108 

 and 2269, in 48 fathoms. 



This species bears considerable resemblance to N. ortiatisshna 

 D'Orb., but the ribs are less numerous, more curved, and the primary 

 ones are much larger and more widely separated, and the shell is less 

 convex. 



Neaera paucistriata Daii. MSS. 



Three living specimens, found in 16 and 17 fathoms, were identi- 

 fied by Mr. Dall as this species. 



