308 PALEONTOLOGY OF NEW-YORK. 



Figures 18 - 17 are illustrations of this speoios. 



Geological formations and localities. This species occurs in calcareous beds in 

 the upper part of tlie Hamilton group, at Eighteen-mile creek ; and in the Tully 

 limestone, near Ovid, in Seneca county. 



Meristella nieta (n. s.). 



PLATE XLIX. 



Shell eubglobose, or very gibbous, short ovate ; the valves subequally 

 convex, marked by a conspicuous sinus in front j hinge-line about 

 two thirds the width of the shell. 



Ventkal valve very gibbous ; umbo prominent, with beak abruptly 

 nasute ; the upper part of the valve marked by a shallow scarcely 

 defined depression, which becomes a deeply marked subangular sinus 

 in front. 



Dorsal valve regularly convex, gibbous in the middle and above ; ante- 

 rior margin broadly sinuate, and the lower part of the valve marked 

 by a narrow median depression. 



Surface concentrically striated, with faint indications of interrupted 

 radiating striae. In the specimens examined the Shell is partially 

 exfoliated, and the entire surface-characters cannot be ascertained. 

 The figures 1 - 4 of Plate xlix illustrate this species. 

 This fossil is referred to Meristella from its general form, the filjrous texture 



of the shell, and the form of muscular area in the ventral valve. 



Geological formation and localitiy. In calcareous bauds in the Hamilton group 



at Delphi, Onondaga county, N. Y. 



Meristella ? 



PLATE XLVII. 

 The illustrations, figures 32 and 33 of this plate, are of casts of what 

 appear to be a species of Meristella from the Chemung group, though 

 no exterior of a similar shell has been found in the rocks of that 

 formation. 



