MONOGRAPH OF THE GENUS STROPHIA. 
117 
placed a little to the right of the center. The upper tooth is well 
developed, being about half as high as the lower, but extends backward 
and makes a turn around the column. 
Margin, produced forward nearly 
as far as the diameter of the shell, 
and is very slightly inclined to the 
right, but not beyend the diameter of 
the shell ; it is thin, about .02 is not 
produced backward, but ends in a 
blunt edge, about the middle of its 
width. The frontal bar is well devel- 
oped and completely interrupts the 
striations which do not appear within 
it. 
Color of shell, externally, reddish 
white, flecked with longitudinal mark- 
ings of reddish brown ; internally, 
rather pale brown, fading into creamy 
white on the margin and frontal bar. Apex, horn color. 
DIMENSIONS. 
Size of ty^pe, .70 by .30. Largest specimen, .95 by .36 ; smallest, 
,52 by .30. Greatest diameter, .38 ; smallest, .27. Longest specimen, 
.95; shortest, .52. 
OBSERVATIONS. 
Individual variation from the type locality seems to consist in 
color mainly, some being more decked, as in S. curtissii, and in size, 
the largest approaching even typical S. curtissii, and are probably 
reversions toward that species but they maintain the nine whirls, 
thin 'margin and other characters given above. There are the 
following well-marked forms : 
No. 1. Form, size, and markings similar to those of the type, 
but the margin is heavier and the upper tooth is absent, but the lower 
is elongated as in the type. Found around the borders of the type 
colony, and constitutes about one quarter of all the specimens 
collected. 
No. 2, differs from the type in being undecked, the color being 
reddish while, in having the striations smaller and more numerous? 
Fig. 31. 
C D 
A, Strophia curtissii nivia, front view of 
type. D, Strophia thorhdikei, front 
viewoftype. B, form No. 3, S. thorn- 
dikei, front view. 0, form No. 4, S. 
thorndikei, front view. 
