Strophia thorndikei Maynard, 1894

Original Description


            Thorndike's Strophia.

FIG. 34, D, front view of type.


            SP. CH. Size, small. Shell, rather thin and light. Striations, present. Whirls, nine. Examined, 2,000 specimens.

            Form of shell, inclined to be cylindrical, the first and second whirls being about equal in diameter, and the third is but little smaller, then the shell slopes rather quickly to a blunt point, forming an angle of about fifty degrees. The striations are rather numerous, twenty-one on the first whirl, not prominent, rather regular, and arranged in lines; they are slightly inclined from right to left, are rather wide, hence are about as wide as the interspaces between them; they are not furrowed but are smoothly rounded.

            Aperture, quite small, inclined to be rounded, and is slightly contracted at the entrance. Lower tooth, quite prominent, .05 high by about .12 long, is set well back, .08, is somewhat elevated and is

p1aced a litt1e 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 beyond 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 developed and completely interrupts the

striations which do not appear within it.

            Color of shell, externally, reddish white, flecked with longitudinal mark­ings of reddish brown; internally,

rather pale brown, fading into creamy

white on the margin and frontal bar. Apex, horn color.


Size of type, .70 by .30. Largest specimen, .95 by .36; smallest,

.52 by .30. Greatest diameter, .38; smallest, .27. Longest specimen,

.95; shortest, .52.


Individual variation from the type locality seems to consist in

color mainly, some being more flecked, 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


            No.2, differs from the type in being unflecked, the color being reddish white, in having the striations smaller and more numerous, twenty-seven to the first whirl; but rather singularly, the margin is heavier. The size is a little larger than that of the type, .80 by .35. The central tooth is greatly elongated, being three times as long as high, bnt the upper tooth is absent. Specimens vary a little, some being larger than the type and some show slight fleckings, others have the upper tooth. I have remarked that the bushes in the cemetery where this shell is found had recently been cut down and left on the ground. Thus is was impossible for me to tell if this unflecked form occurred on them, but I should judge that it might have lived above the ground before it was distributed. As I could not assign a locality for it I have given it as a form only of S. thorndikei.

            No. 3, is a remarkable form of shell. Short, shell with eight whirls only, top shaped, with the upper whirl the largest, and with the aperture nearly oval with the lower tooth central in position (see fig. 34, D, front view. the size is very small, .52 by .30, and the fleckings are about as in typical thorndikei. I found this dwarf form in the very midst of the colony of S. thorndikei, but living on the ground, and among them were mongled some typical S. thorndikei. There were about one per cent. of both Nos. 2 and 3 in proportion to typical S. thorndikei.

            No. 4 is a  slender, cylindrical form with the first three whirls equal in diameter and the margin thrown well over to the right, the upper tooth missing, and the frontal bar is oblique and inclined to the right; very dark in color, with heavy fleckings, and the color within is also very dark brown. Although I have but a singles specimen only of this form I have considered it remarkable enough to mention. Fig. 34, D.

            No. 5. Of the form and size of the white form, No. 2, but pale brown throughout, slightly flecked on the striations with white. I have a single specimen only of this form, but mention it as it is remarkable.


            There is a path which crosses the cemetery from the entrance that is quite frequently used, and thus being kept free from herbage, it forms a kind of barrier which prevents a mollusk like Strophia from crossing readily. S. curtissii occupied the land to the west of this path, but midway between the gate of the cemetery and the hill of which I have spoken in the account of the preceding species I found the colony of S. thorndikei, but to the eastward of the pathway which thus isolated them from the Strophias on the western side.

            Most of these shells were on the ground or on the grass near it and occupied in all about one hundred square yards, being thus extremely limited in distribution. The colony had recently been much disturbed by the cutting of the bushes over and about it and some specimens had been thrown across the path, thus it was difficult to trace out the location of the various forms. Thorndike's Strophia was quite abundant in this place, but I could not trace it elsewhere and am sure that it did not extend its range beyond the borders of the path to the westward, nor beyond the cemetery wall to the eastward, and not over ten yards north and south. All specimens were hybernating when we found them.

            I have named this species for Dr. T. W. Thorndike, of Boston, an enthusiastic naturalist, who accompanied me on the expedition to the Bahamas."

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