270 
PALAEONTOLOGY OF NEW YORK. 
A small specimen preserving both valves has a length of 53 mm., height 
38 mm., and depth of both valves 13 mm. A large right valve has a length 
of 80 mm., and a height of 36 mm. 
This species is distinguished by the comparatively great width of the valves, 
the rounded ventral margins and the compressed form of the shell. It resem¬ 
bles M. Clarens in general form, but the posterior end is not so regularly rounded, 
and the valves are higher than in that species. In M. complanata the umbo is 
more prominent, the anterior end narrower and rounded, the posterior end not 
so regularly rounded, and the posterior muscular impression is farther within 
the cavity of the valve. 
Formation and locality. In the Schoharie grit, Schoharie, N. Y. 
Modiomorpha regularis, n. sp. 
PLATE XXXV, FIG. 12. 
Shell above the medium size, elongate, sub-elliptical; length less than twice 
the height; anterior margin abruptly rounded; ventral margin broadly 
curved; posterior margin regularly rounded. Anterior end somewhat 
narrow. 
Valves depressed convex; the point of greatest convexity being near the 
middle of the length. 
Hinge-line longer than the height of the valve, very slightly oblique. 
Beaks depressed. Umbonal region moderately convex. 
Test marked by strong concentric laminae of growth. Interior unknown. 
A right valve has a length of nearly 70 mm., and a height of 40 mm. 
This species differs from M. Schoharie in its more elongate form, longer liinge- 
line and more rounded anterior end. It somewhat resembles certain forms of 
M. mytiloides, but the hinge is not so oblique as in that species, the anterior end 
is broader, and the ventral margin is more regularly curving. 
Formation and locality. In the Schoharie grit, Schoharie, N. Y. 
