"STROPHIA PERPLEXA Novo.
Ridged Strophia.
Plate VII, 15 & 15A, shell. and .Fig. 7, A left side; B front.
DESCRIPTION.
SP. CR. Size, medium. Shell, thick and rather heavy. Striations, assume the form of irregular ridges. Whirls, 11. Examined 300 specimens.
Form of shell, inclined to cylindrical, the first two whirls being equal in diameter and the third is but little smaller. From the third whirl, the shell slopes rapidly to a rather blunt point, making an angle of about 60 degrees. The striations are represented by irregular, slightly elevated ridges, that are rather more prominent on the upper portion of the shell. Some of the ridges are a little flattened on the top and furrowed.
Aperture, rather small and narrows within. Lower tooth, prominent, .05 high, .24 long, and its position is just a little to the right of the centre; the upper is not as prominent but measures .05 and makes a complete turn around the column.
Margin, not produced forward beyond the diameter of the shell, is not inclined to either side, is considerably thickened, measuring .06, and the outer posterior portion is slightly produced backward, but there is no prominent edge. The frontal bar is well developed and the striations do not appear within it.
Color of shell, externally, white; internally, pale purplish brown which gradually fades into yellowish white on the teeth and walls within the aperture.
DIMENSIONS.
Size of type, .90 by .40. Largest specimen, 1.00 by .43; smallest, .78 by .34. Greatest diameter, .43; smallest, .34. Longest specimen, 1.07; shortest, .85.
OBSERVATIONS.
While a large percentage of the specimens of this species clesely resemble the type, there is a. tendency to assume a more pointed form with a less number of ridges, thus bearing a somewhat close resemblance to S. acuta, but I have never seen a S. perplexa that could not be separated from that species by the presence of more or less ridges, and by the greater thickness of the shell and its whiter color. On the other hand, some specimens exhibit an inclination to assume striations, irregular and widely separated, thus approaching S. intermedia, but the striations are never decided enough for intermedia. In possessing these characters, however, the Ridged Strophia is between the Pointed and Intermediate Strophias, and at first occasioned me considerable perplexity, as it appeared to form a connecting link between the two. But as S. perplexa occurs on Cayman Brae, apart from other Strophias, and is thus widely separated from either of the two closely allied shells, and
like many species having apparently obscure characters, taken individually, yet while in mass, show strong differences, I soon saw that I could not consistently do otherwise than to consider it a distinct species, as above described. .
Known from all other species, by the absence of striations but presence of ridges, white color, and heavy shell.
DISTRIBUTION AND HABITS.
The Ridged Strophias occur on the island of Cayman Brae in a barren, rocky section, about two miles from the west end of the key, and a quarter of a mile from the south shore. They were restricted to a very limited area, and I found them clinging to low herbage or to the naked rock, in almost every instance, exposed to the burning rays of a tropical sun."
