102 NEW YORK STATE MUSEUM 



would seem to differ from the western form mainly in the some- 

 what more elongate form, the less evenly rounded anterior and 

 posterior margins and the more posterior position of the beak. 



Ctenodonta radiata nov. 

 PL 6, fig. 6 



Description. Shell thin, of medium size, subovate, three-fourths 

 as high as long, anterior margin broadly rounded, posterior oblique 

 and nearly straight or gently convex in the dorsal part and rather 

 sharply rounded below; the ventral margin is but slightly curved. 

 Beaks very little prominent, situated a little more than one-fourth of 

 the entire length behind the anterior extremity. Shell compressed- 

 convex, more convex in posterior half, culminating posteriorly of 

 center in the broadly rounded umbonal ridge. Surface markings 

 consisting of a few growth varices and fine concentric lines, which 

 are crossed on the posterior portion by straight radiating lines. 

 Hinge and muscle scars not observed. 



Position and locality. Dark gray to olive, partly sandy shales of j 

 Snake Hill beds. Snake hill, Saratoga county, N. Y. 



Remarks. This is one of the largest Ctenodontas of the Snake j 

 Hill beds ; it is readily distinguished from the • others by its size, 

 rthe thinness of its shell and above all the radiating lines. These 

 latter, as several other characteristic features, it has in common 

 with C. calvini Ulrich, a western Richmond (Maquoketa) 

 species. It differs from that younger species in being relatively 

 shorter, narrower behind and higher in front. 



Ctenodonta recta nov. 

 PI. 6, fig. 7, 8 



Description. Shell small, compressed, convex, subtriangular in 

 outline, one-third longer than high ; beak rather large but little i 

 prominent, incurved, turned slightly backward, situated about mid-| 

 way between the extremities ; anterior margin well rounded, posterior f 

 more abruptly, and ventral one broadly. Anterior dorsal margin 

 slightly convex, posterior one distinctly concave, impressed so as 

 to form a small lunette. Surface of shell almost uniformly convex, 

 highest subcentrally ; with a few well-marked varices of growth and 

 fine concentric lines. Hinge plate and muscular scars not observed. 



Position and locality. In the dark sandy shale of the Snake Hill|^ 

 beds at Snake hill and elsewhere. 



