42 NEW YORK STATE MUSEUM 



Coelospira concava Hall 



Plate 5, fig. 23-26 



1892. Coelospira sp., Clarke, op. cit. p. 413 



For figures see Paleontology of New York. v. 3, pi. 38, fig. 1-7; 

 v. 8, pt 2, pi. 53, fig. 20-23 



This little shell agrees in size and contour with the common 

 Helderbergian species, but seems never to bear more than 12 plications, 

 while in normal examples of the species the number may vary from 

 10 to 16. 



The interior of the pedicle-valve bears a short median septum 

 dividing two posterior muscular scars: at the middle of the valve it 

 bifurcates and seems to inclose the impression of an anterior muscular 

 pair, an arrangement similar to that seen in Coel. Camilla of the 

 Onondaga limestone. 



This species is less common than Coel. dichotoma. 



Coelospira dichotoma Hall 



Plate 5, fig. 27-32 



For other figures see Paleontology of New York. v. 3, pi. 103, fig. 3 a-e 

 Very abundant, occurring in large, well denned examples through- 

 out the beds. This species is readily recognized both by its 

 size, which at maturity is the largest attained by species of this genus, 

 and by the duplication of its plications. The interior of the pedicle- 

 valve shows a median septum extending for more than one half the 

 length of the shell and dividing an elongate muscular area. 



Leptocoelia flabellites Conrad 



Plate 5, flg. 33-36 



1892. Leptocoelia flabellites Clarke, op. cit. p. 415 



For other figures see Paleontology of New York. v. 3, pi. 103b, fig. 

 la-g; 106, fig. la-f; v. 8, pt 2, pi. 53, fig. 40-46, 53 



The specimens of this species are in pretty close agreement with 

 typical examples from the arenaceous Oriskany. A difference which is 

 observable in all examples is a slight convexity of the brachial valve, 

 specially pronounced on the anterior region by a deflection of that valve. 



