406 PALEONTOLOGY OF NEW YORK. 



This form is comparatively more elongate than any other species. In its 

 strong post-cardinal fold it may be compared with S. cuneatus and S. subtortuo- 

 sus of the Hamilton group, but it has no anterior depression nor sinuosity of 

 the pallial margin. The produced anterior end and regularly curving basal 

 margin are distinguishing characters. 



Formation and locality. In the Waverly group, at Warren, Pa. 



Sphenotus Telamon, n. sp. 



PLATE XCIV, FIG. 1. 



Shell large, elongate sub-elliptical ; length more than twice the height ; basal 

 margin very gently curved. Posterior extremity narrowly rounded below 

 and obliquely truncate above. Cardinal line very slightly arcuate. Ante- 

 rior end declining from the beaks and somewhat narrowly rounded below. 



Valves gently convex in the lower and posterior portions, becoming gib- 

 bous in the middle. 



Beaks at about the anterior fourth, incurved. Umbonal slope obtusely 

 angular above, extending to the post-inferior margin. Cardinal slope wide, 

 marked along its centre by a distinct fold, which extends to the upper pos- 

 terior margin. 



Surface marked by fine concentric strias, which on the middle and poste- 

 rior portions are irregularly fasciculate, forming distinct undulations of the 

 surface ; anterior end with regular sub-angular ridges. The striae at the 

 post-inferior extremity are almost rectangularly recurved. 



The specimen described has a length of 59 mm. and a height of 26 mm. 



This species in its general external characters resembles Allorisma, but the 

 limitation of the post-cardinal slope by the umbonal angle and the distinct pli- 

 cation along the middle of this area are characteristic features of Sphenotus, 

 and on this account it is placed under that genus. 



Formation and locality. In the Chouteau limestone of the lower Carbonif- 

 erous, in Cooper county, Mo. 



