580 NEW YORK STATE MUSEUM 



gulation probably exaggerated by lateral compression). Growth 

 lines obliquely pennately arranged, turning subparallel to the 

 margin in the flat marginal border. A faint depression and ridge 

 running parallel to the keel are observable on either wing. The 

 longitudinal rows of pustules are very prominent, wherever the 

 Bhell is exfoliated. 



While this valve, in its long, lanceolate form and long, oblique 

 basal margins, reminds one of the carina of S c a I p e 1 1 u m , 

 it lacks the angles, separating the tectum from the parietes and 

 intra-parietes, which are characteristic features of that genus. 

 The possibility that this valve could be a laterally compressed 

 and extenuated tergum is excluded by its symmetric form. 



3 Rostrum. 'Small, thick-ghelled, symmetric, forming two 

 sides of a tetrahedron; apex incurved (flattened in the figured 

 specimen by compression, as indicated by a break); keel strongly 

 elevated, angular, broad; surface with strong unequal growth 

 lines running parallel to the basal margin. 



This valve bears a strong resemblance to the rostrum of P o 1 - 

 licipes carinatus, which, however, has a flat-topped keel. 



4 Upper latus. Small, little convex, six-faced, eight-sided, 

 thick-shelled; two middle faces forming a high, basally widening 

 keel; other faces nearly flat; surface with fine, concentric growth 

 lines; broad, concentric undulations, crossed by fine radial striae, 

 on the two extreme faces and along the basal margin. 



This valve has been termed an upper latus on account of its 

 similarity to the upper latera of Scalpellum quadratum 

 and Sc. fossula. The general form of this valve is very 

 much like that of some of the problematic Pterothecas de- 

 scribed by Hall from the Trenton, and by Barrande from the 

 Bohemian Siluric. As our specimen however, agrees in the 

 nature of its shell with the valves of P o 1 1 i c i p e s with which 

 it is associated and can ibe referred to a part of the capitulum of 

 this crustacean, it seems at present more profitable to unite it 

 with the latter than to compare it with the still entirely problema- 

 tic P t e r o t h e c a . 



