488 PROCEEDINGS OF THE ACADEMY OF [June, 



Potamides caobasensis n. sp. Fig. 2. 



The shell is conic-turrit e, rather solid, 6+ whorls remaining, the 

 summit truncate, closed by a convex plug. There 

 is a prominent ridge forming a narrow, hori- 

 zontal ledge below the suture. Below this ledge 

 the surface is flat, smooth and vertical. The 

 last whorl is rounded at periphery and base. The 

 aperture is injured, but apparently formed much 

 as in P. roumaini. 



Length of broken shell 23 mm. 



A peculiar species, distinguished by its smooth 

 whorls, prominent below the suture. 

 Natica rugosa Gmel. 



A single specimen, found with the preceding. 



Potamides caobas- Area websteri n. sp. 



ensis - Shell of moderate size, the alt. contained nearly 



1^ times in the length, inflated, thick and heavy, with strongly ele- 

 vated prosogyrate beaks. Left valve with 32 strong, abruptly elevated 

 ribs which are closely sculptured with transverse nodules, and are 

 a little wider than their intervals. On the posterior slope the ribs 

 lose the nodules, gradually decrease in elevation and are rounded, 

 becoming quite weak near the hinge border. The basal margin 

 converges posteriorly towards the hinge line, and is full and convex 

 anteriorly; anterior end rounded, posterior end convex, obliquely 

 subtruncate. Hinge bearing about 2,438 teeth, an irregular tooth 

 or two near the middle, terminal teeth larger but straight or nearly 

 so. Cardinal area short and wide, marked with several resiliary 

 grooves forming 3 or 4 concentric lozenges. The terminal and basal 

 margins of the valves are deeply fluted, and the interior conspicuously 

 striated. 



Length 42.5, alt. 34, diam. of left valve 17.3 mm. ; length of hinge- 

 line 28.5 mm. 



This fine ark is closely related to the recent A. chemnitzii but 

 differs by the greater number of radial ribs and the heavier, larger 

 shell. ^4. staminea Say is also related. It is represented by numerous 

 left valves and fragments, some of the latter indicating that it attains 

 a larger size than the type specimen. The two valves are presumably 

 alike in sculpture. 



In several valves in the lot, the cardinal area is decidedly narrower 

 than in the type. These may possibly represent another species. 

 Type No. 1.312 A. N. S. P. 



