348 PALEONTOLOGY OF NEW YORK. 



Valves convex posteriorly and below, becoming gibbous in the middle and 

 upper portion. 



Beaks at about the anterior third, prominent, rising but little above 

 the hinge-line. Umbonal region regularly convex. Umbonal slope convex 

 or sometimes flattened, giving an obscure truncation to the posterior 

 extremity. (Fig. 43 exaggerates this feature, which is more properly shown 

 in fig. 44.) 



Test thin, marked by fine, close, concentric striaB with sharp lamellose 

 elevations at irregular intervals. The characters of the interior are shown 

 in figs. 45 and 46 of plate 1. 



Three specimens measure respectively 35, 30 and 22 mm. in length, and 

 18, 16 and 12 mm. in height. 



This species is more symmetrically ovate and gibbous than any of the pre- 

 ceding forms. It is easily distinguished from P. attenuata, with which it is 

 associated, by its shorter and more gibbous form and absence of mesial con- 

 striction. 



Its mode of occurrence at Hillsdale, Mich., is in the condition of casts, which 

 preserve some impressions of the finer strisB, while the place of the stronger 

 lamellae is marked by narrow, concentric sulci, suggesting the name given by 



Mr. CONEAD. 



A comparison with the type specimens of Leda nuculiformis, Stevens, leaves no 

 doubt of its identity with the species originally described by Mr. Conrad as 

 Nuculites sulcatina. 



Formation and localities. In the Waverly sandstone at Richfield and Newark, 

 0. ; also occurring at Battle Creek, and abundantly at Hillsdale, Mich. 



Pal^oneilo ? DOBiA, n. sp. 



PLATE XCIII, FIG. 15. 



Shell large, elongate-ovate ; length and height as five to three ; basal margin 

 regularly curving for more than the anterior half of its length, slightly sinuate 

 to the posterior extremity, which is narrowly rounded. Anterior end short, 

 contracted beneath the beak and rounded below. 



