136 MONOGRAPH OF THE GENUS STKOPHlA, 
pletely interrupts the striations that there is no trace of them 
within it. 
Color of shell, dull white throughout, without markings of any 
kind. Within, flesh color, fading into white on the teeth and margin. 
DIMENSIONS, 
Size of type, 1,37 by ,57. Largest specimen, L37 by .65, 
smallest, 1.10 by .46. Greatest diameter, .65; smallest .46. Longest 
specimen, 1.40; shortest, 1.10. 
OBSERVATIONS. 
The type form is very constant, pure individual variation being: 
but slight. There is an inclination toward a more cylindrical form 
with the first three whirls equal, and some specimens show a slightly 
thickened margin, but as a rule, this is as in the type, and no thicker 
than the shell. The whirls vary in this form from ten to twelve. 
There are however, the following well-marked forms : 
No 1. About the form and size of the type, but with more 
numerous striations, twenty-five to the first whirl. The margin is 
thinner, with the edge sharpened, and the aperture smaller and more 
contracted. The color is ashy brown, with the striations creamy 
white, and the color within is rather dark, purplish brown. In this 
form there are individuals with slightly coarser striations, 20 to 22 to 
the first whirl. These usually have a thickened margin and a more 
cylindrical form. This form is not very common, being about one per 
cent of the whole. 
No. 2 is a small form, 1.10 by .47, but with ten whirls, and with 
only sixteen striations to the first whirl, and the first three whirls are- 
equal in diameter. Otherwise as in the type. 
No. 3. Cylindrical, with eleven whirls, the first three of which 
are equal in diameter. The striations are a little less numerous than 
in the type, but the margin is rounded, but not thickened. There is a 
slight individual tendency in this form to assume, with fewer striations, 
the thin sharpened margin seen in the next species, S. grayi, but 1 
can find no fewer than eighteen striations in any specimen, therefore it 
is the extreme form is not typical S. grayi. These are about one 
half per cent of the whole of this form. 
No. 4 is a remarkable form typically and, in fact, an incipient 
species, but with two many gradations yet to permit a consistent 
