MOLLUSCA. 529 



Liopistha kiimmeli n. sp. 

 Plate LVIII., Fig. 3. 



Description. — The dimensions of a large right valve are: 

 length, 21 mm.; height, 15 mm.; convexity, 4.5 mm. Shell sub- 

 ovate in outline, beaks central or a little in advance of the center, 

 strongly incurved ; antero-cardinal margin curving gently down- 

 ward anteriorly from beneath the beak tad passing regularly 

 into the broadly rounded anterior margin;. basal margin broadly 

 rounded, becoming straighter posteriorly and sloping upward 

 to the most posterior extremity of the shell which is above the 

 mid-height; posterior extremity rather sharply rounded into 

 the post-cardinal margin which is straight and horizontal. Sur- 

 face marked by about 20, simple, subangular, radiating costas, 

 subequal in size, but becoming somewhat smaller anteriorly; 

 upon the cardinal slopes the costae become much fainter or even 

 obsolete, the smooth area being broader " behind than in front; 

 upon the umbo' and towards the beak, more or less faint con- 

 centric undulations cross the radiating ribs, but these become 

 obsolete before reaching the middle oif the shell in adult ex- 

 amples; impressions of the exterior show in addition to the 

 radial and concentric markings already described, fine concentric 

 lines of growth. 



Remarks. — This species differs from L. alternata which occurs 

 in the same horizon, in the absence oif the alternating cost^, and 

 in the presence of the concentric undulations towards the beak. 

 It agrees more nearly with L- protexta from the Navesink marl, 

 but the radiating costse are coarser and less numerous, and that 

 species also lacks the concentric undulations. In the presence of 

 these concentric undulations, the species approaches the mem- 

 bers of the genus Cyme'lla in which the concentric markings are 

 more conspicuous than the radial, but the much stronger radial 

 markings suggests a closer relationship to the members of the 

 genus Liopistha- 



Formation and locality. — ^Merchantville clay-marl, near James- 

 burg (139), lycnola (163). 



Geographic distribution. — New Jersey. 



34 PAL 



