STROPHODONTiE OF THE UPPER HELDERBERG GROUP. 
93 
StropSiodonta ine<pi§triata* 
PLATE XII. 
Strophomena inequistriata : Conrad, Jour. Acad. Nat. Sci. Phila., Vol. viii, pa. 254, pi. 14, f. 2. 
This species was originally described by Mr. Conrad from the Moscow 
shales of the Hamilton group, where it occurs in considerable numbers. 
Among the collections from the Corniferous limestone are a few specimens 
quite undistinguishable from those of the Hamilton group, and which I have 
referred to this species. 
The figures 6 & 1 of Plate xii 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 S. patersoni; but the specimen is much more gibbous 
than any authentic individuals of that species. 
Farther illustrations are given on Plate xvm. 
Geological formation and locality. In the Corniferous limestone, near Cale¬ 
donia, Livingston county. 
Strophodonta ampla. 
PLATE XIV. 
Strophomena ( Strophodonta) ampla : Hall in Tenth'Report on the State Cabinet, p. 111. 1857. 
Strophomena ampla : Billings in Canadian Journal. 
Strophomena ampla : Geological Report of Canada, p. 368. 1863. 
Compare Strophodonta headleyana, S. punctulifera, and S. cavumbona : 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, 
