395 



Meris. 



(Meristella unisulcata, continued.) 

 Villa. ". 



m c. 



HaJT^^m^ IS- fi. At, .Rh. /U 2. . «^sy-=-7>/ z 



near the beak, as shown in the figure, while there is a second 

 fold on the side of the shell. Fig. 19 is a specimen from the 

 Upper Helderberg limestone of the West ; in which the fold is 

 sharp and clearly defined, slightly oblique, and intermediate 

 to the former two; the specimen is more gibbous than those 

 from the limestone of New York. Figs. 20 and 21 are ventral 

 and dorsal views of a large specimen from the limestone of 

 New York; fig. 22, profile of the same; fig. 23, front view of 

 the same. Fig. 24, interior of the dorsal valve, showing a 

 median septum, cardinal process, teeth, sockets, and bases of 

 the crura. Fig. 25, interior of ventral valve, showing the teeth 

 and muscular impression. (Figs. 24 and 25, * ^ ^ ^ from 

 the limestone of the Falls of the Ohio.) Hall proposed for 

 the Hamilton form M. unisulcata^ var. hiplicata; and the 

 western form M, unisulcata^ var. u^niplicata. — VIII a^ c. 



Meristella ? found in the Oriskany shales (here the 



only representative of VII) south of Port Jervis, in New 

 Jersey. G6, p. 123, on Pike and Monroe Cos., Pa. — VII. 



Meristella ? found by 0. E. Hall among Oarll's Che- 

 mung collections in N. W. Pa. — VIII g. 



