174 
MONOGRAPH OF THE GENUS STROPHXA. 
DIMENSIONS. 
Size of type, 1.12, by .43. Largest specimen, 1.17 by .43; small- 
est, .90 by .40. Greatest diameter, .43; smallest, .40. Longest 
specimen, 1.17; shortest, .85. 
OBSERVATIONS. 
Individual variation is great, and the most noticeable is toward 
producing a white form, which is clearly a reversion toward typical S. 
pilsbryi, in fact, this form grades directly into the parent stcc c. 
Another variation, which may be considered as progressive, is 
toward producing a shorter, thicker form, with nine whirls and with 
numerous striations, thirty to the first whirl, they are regular, and not 
wider than the interspaces, and the first whirl is as long as the first 
five, while the aperture is inclined to be rounded, and more in the 
centre of the shell than in the type. The color is also dark, nearly 
uniform ashy brown, but with central tooth as in the type. I notice 
this form particularly as I believe that it will be found somewhere, at 
some time, as an established species. 
Directly opposite this is a larger form, more cylindrical, with the 
first three whirls equal in diameter, and with the transverse mottlings 
more pronounced. This form seems to mark the direction in which 
the sub-species is trending to establish a full-ranked species. Occa- 
sionally a specimen will show a double margin. 
As will be seen, the characters which mark this fine sub-species 
are, first, and most important, the elongated central tooth projected 
well forward, toward the frontal bar, a remarkable character and one 
which I have never seen so prominent in any other species of this 
genus; second, the form of the margin, with its oblique bar; thirdly, 
the peculiar mottlings, recalling those of S. mumia. Besides, we have 
the usual characters which almost alw ays accompany the evolution of 
a dark, mottled form of shell from a white form, namely, the thicken-, 
ing of the shell and contraction of the margin. All of these 
characters in combination, together with the fact that this form has 
a location of its own, go to make up good and sufficient specific 
characters and I would so consider them, but there is yet too great 
a number of specimens which must be considered as intermediate. 
HABITS AND DISTRIBUTION. 
This strongly marked sub-species occurs on the bushes of the 
western and larger portion of the Goat Key, (E, in the chart, fig. 55,) 
