STROPHODONT^ OF THE UPPER HELDERBERG GROUP. 93 



Stropliodonta inequistriata. 



PLATE XII. 

 Strophomena inequUtriata : Conbad, Jour. Acad. Nat. 3ci. Phila., Vol. viii, pa. 254, pi. 14, f. 2. 



This species was originally described by Mr. Conead from the Moscow 

 shales of the Hamilton group, where it occurs in considerable numbers. 



Among the collections from the Comiferous limestone are a few specimens 

 quite undistinguishable from those of the Hamilton group, and which I have 

 referred to this species. 



The figures 6 & 7 of Plate xn are ventral and dorsal views of a well-marked indivi- 

 dual, which is of the ordinary size of the species. 



Figure 8 is a profile view of a very gibbous specimen, which has a more strongly 

 marked surface, resembling 8. patersoni ; but the specimen is much more gibbous 

 than any authentic individuals of that species. 



Farther illustrations are given on Plate xviii. 



Geological formation and locality. In the Comiferous limestone, near Cale- 

 donia, Livingston county. 



Stropliodonta anipla. 



PLATE XIV. 



strophomena (Strophodonta) ampla : Hail in Tenth Report on the State Cabinet, p. 111. 1857. 

 Strophomena ampla .- Billings in Canadian Journal. 

 Strophomena ampla : Geological Report of Canada, p. 868. 1863. 



Compare Strophodonta headley una, S. puncluli/era, and S. cavunibona : Pal. New York, Vol.iii, 



pp. 186-188. 



Shell large, broad, semioval or subsemicircular ; length from two- 

 thirds to three-fourths as great as the width; hinge-line equalling or 

 longer than the width of the shell below, with extremities often a 

 little salient. Ventral valve concave, with a slight convexity about 

 the umbo, and very rarely a mesial elevation extending from the beak 

 nearly to the front of the shell. Dorsal valve convex in the middle. 



