414 PALAEONTOLOGY OF NEW YORK. 



Pliolidops oblata (n. s.). 



PLATE III, FIG. 10. 



Shell suborbicular, somewhat flattened on the upper margin, discoid or 

 depressed convex ; the length and width about equal ; muscular area of 

 the interior small, circular, and divided through the middle by a longitu- 

 dinal septum. External surface unknown. 

 In general aspect this species somewhat resembles P. arenaria, but differs very 



materially in the form of the muscular impression. 



Geological formation and locality. In the shales of the Hamilton group, at Car 



tor's Mills, four miles south of Aurora, Onondaga county, N. Y. 



Pliolidops ? linguloides (n. s.). 



PLATE III, FIG. 11. 



Shell broadly ovate, with an obtusely pointed beak, which is apparently 



terminal. 

 Surface covered by rather closely arranged, strongly lamellose concentric 



lines of growth, which reach the margin of the valve near the beak. 

 Length of shell sixty-two hundredths of an inch ; greatest width, fifty-six 



hundredths of an inch. 



This species differs from any of the described forms of the genus Pholhwps in 

 its terminal beak and subnacreous shell. There may be some doubt regarding the 

 propriety of its reference to this genus, but at present no other group seems so well 

 adapted to its reception. 



Oeological formation and locality. In concretionary layers of the Hamilton 

 shales, on Canandaigua Lake, New York. 



Stropliomena rhoniboidalis ? 



PLATE XV, FIGS. 15, 16. 



Specimens of shells having the characters of this species have been 

 obtained among a collection from Mallet's Creek, two miles north of York 



