130 
MONOGRAPH OF TIIE GENUS STROPHlA. 
Fig. 39. 
central in position, a little elevated, and set back about once its 
length. The upper tooth is about half as high as the central, is placed 
low, being but little above the top of 
the lower tooth. 
Margin, produced forward as 
far as the diameter of the shell, is 
slightly inclined to the right, a trifle 
beyond the diameter of the shell. It 
is considerably thickened (.07), with 
the edge projected backward, and 
shapened, but not rolled downward. 
The frontal bar is quite well developed, 
and interrupts the striations, which 
are, however, slightly indicated within 
it. 
Color of shell, externally, deep 
ashy brown, with the striations creamy white ; internally, also brown, 
a little paler than on the outer surface, becoming creamy white on the 
tooth, margin and frontal bar. 
At ' 
V - 
V ■ 
B A 
Strophia coryi, A, front. view, B, sic’e 
view, of type. 
DIMENSIONS. 
Size of type, 1.00 by .40. Largest specimen, 1.12 by .42; small- 
est, .62 by .36. Greatest diameter, .45 ; smallest, 36. Largest 
specimen, 1.12; shortest, .62. 
OBSERVATIONS. 
The type form is very abundant, proportionately, and there is 
comparatively little variation that can be considered as purely 
individual. What little there is consists in a thinner or thicker margin, 
and slightly finer or coarser striations, but there are five distinct 
forms developed, which areas follows: 
No. 1 is an elongated cylindrical form with the first four whirls 
equal in diameter, and a thinner margin. This form grades directly 
toward S. cinerea, and I have three specimens that are direct 
reversions toward that species. Size, 1.10 by 1.36. 
No. 2. This is a singular form, nearly pure white in color, 
shorter, with nine whirls only, faintly yellowish within, and slightly 
tinted with brownish between the striations. Size, .97 by .47. This 
form recalls the white No. 3, which has been evolved from S. cinerea 
