times the breadth. I cludent and carinal margins are both strongly convex. The whole 



tpitulum by a chitinous membrane, with the exception only of the apex of the tergum. 



ves is mostij very indistinct: though the largesl specimen of Station 45 

 ired the shape of the latera is much more distincl in the smaller specimen of the 



Station Hence f<>r the description of these valves the smaller specimen has been mostly 

 mai 



The scutum lias the occludent margin convex and the tergal margin slightly hol lo wed 



out. The calcified part is formed of two segments united at the apex: the one the occludent 



ider ai the base and narrower towards the upper extremity; the other the 



ter nds along the tergum, is very narrow and shows the same width over its 



whole length. 



Tl um has the calcified part V-shaped: a shorter and narrower occludent segment 



and a slightly broader and longer carinal segment having their point of junction al the apex of 

 the valve. Along the occludent segment the chitinous covering forms a cushion-like investment, 

 the free margin "I" which is stronglj arched. The apex of the tergum is recurved, bent towards 

 the carinal side of the capitulum. 



The carina has the umbo at some distance from the apex. The part above the umbo 

 is quite covered by the chitinous membrane. the roof of the part underneath the umbo is covered 

 by a thin membrane only. hs width increases distinctly, but not very strongly from the umbo 

 downwards; its margins develop int<» distinct ridges. The sides are rather broad especially in 

 the uppermost part; its limits cannot, however, be made out distinctly. 



The upper latus is broad, trapeziform, the tergal and basal margins running about 

 parallel to each other. The scutal margin joins the tergal margin in a rounded or truncated angle 

 which extends t<> the extremity of the tergal segment of the scutum. The umbo is near the apex. 



The rostral latus is narrow or low. The basal margin is shorter than the scutal 

 margin, the lateral margin slightly convex. The rostral margin of the two rostral latera only 

 meet one another at the upper extremity. A triangular space remains between the two vah 

 which is covered by chitinous membrane only: this is most probably the place for the rostrum 

 if it wi ent as .1 calcified valve. 



The infra-median latus has the umbo near the base. Its general shape is that of 

 a tall win< almost without stalk, with a smal! and narrow foot and the upper part wide. 



The carinal latus has the umbo at the bas.-, projecting beyond the line of the carina. 

 The carinal margin is strongly hollowed out; further, there can be distinguished a short and 

 straight upper margin, a slightly hollowed out lateral margin and a somewhat convex basal margin. 



The peduncle is cylindrical, compressed laterally. The scales on the surface are rather 

 broad but not very prominent. They are numerous but they are not placed in regular longi- 

 tudinal n.v. 



Size. The size of the largest specimen was 28 mm total length and 21 mm. length of 

 pitulum. 



! the specimens is attached to a little piece of the shell of a Gastropod mollusc, 

 the other to a small black stick the nature of which is unknown to me 



71 



