120 
MONOGRAPH OF THE GENUS STROPHIA. 
quite near the frontal bar, about .07 ; h is not elevated ; the upper is 
represented by a slight protuberence. 
Margin produced forward as far as the diameter of the shell, 
slightly inclined to the right a trifle beyond the diameter of the shell, 
is thickened only on the left side, and here but slightly, about .Go. On 
the right it is reduced into a sharpened edge that projects forward ; on 
the left the margin is smoothly rounded, but behind it is developed a 
roughly sharpened lateral edge. Hie frontal bar is narrow but 
prominent, projecting well forward, completely interrupting the 
s libations. 
Color of shell, pale brown, somewhat mottled with white, but with 
the striations ivory white. Internally, light brown, becoming a little 
paler on the margin. 
DIMENSIONS. 
Size of type, 1.15 by .45. Largest specimen, 1.15 by .49. 
smallest, .83 by .37. Greatest diameter, .50 ; smallest, .36. Longest i 
specimen, 1.23 ; shortest, .83. 
OBSERVATIONS. 
There is considerable individual variation even in the type locality 
of this Strophia, and, judging from my past experience with this 
species, which extends over a period of about ten }eais, thete is some| 
danger of the type form becoming extinct. Of this matter, however, 
I shall be able to speak more positively, I trust, in my next instalment 
of this Monograph, the inclinations being to a form with coarser 
striations and fewer ot them. There are also three decided forms 
which are as follows : 
No. 1 is a small form, .83 by .37, with numerous striations, 
twenty-nine to the first whirl; aperture, more contracted, with a 
thinner margin and with the color white, slightly mottled with very 
pale brown. This form occurs in the type locality, and forms about 
fifty per cent, of the whole number found. 
No. 2 is about the same size and form of the type but much 
darker in color, the interspaces being dark brown, and the striations 
pale brown ; the interior is also dark brown, pale on tooth and margin, 
nearly white on low^er side of frontal bar. The striations are narrower, 
being about one half the width of the interspaces. This form rc?urs 
along the beach of Middle Bay, Hog Island, east of the type locality, 
and is not very common, being about five per cent, of the type form. 
