Strophia pumilia Maynard, 1894

Original Description


Short Strophia.

FIG. 44. B, front view of type.


            SP. CH. Size, rather small. Shell, heavy. Striations, present. Whirls, nine. Examined, fifty specimens.

            Form of shell, a short cylinder, with the first three whirls about equal in diameter, the fourth is somewhat smaller, then the shell slopes quickly to an abrupt point, forming an angle of seventy-­five degrees. The striations are few, eighteen to the first whirl, not prominent; rather regular, but not arranged in lines; they are nearly straight, especially on the two upper whirls, but on the remainder of the shell are slightly inclined from right to left; they are narrow. being only about half as wide as the interspaces between them, are

rounded, and although not furrowed, are not particularly smooth.

            Aperture, rather small, inclined to be rounded and open. Lower tooth rather prominent, about .03 high and about twice as long as high, is a little elevated is set back about  once its length from the irontal bar, and is about central in position. Upper tooth present, but very small and elevated above the top of the lower.

            Margin, not produced forward quite as far as the diameter of the shell, and although placed a little to the right of the center of the shell is not inclined to the right. The edge is rounded, and considerably thicker than the shell behind it, but is not rolled backward. The frontal bar is developed well enough to completely interrupt the striations, but projects very slightly beyond them.

            Color, dull white throughout, externally; internally, pale brown becoming white on the teeth and margin.


            Size of type, .90 by .42. Largest specimen, 1.08 by .45;

smallest, .95 by .37. Greatest diameter, .50; smallest .37. Longest specimen, 1.03; shortest, .85.


            Variation lies between a margin as thin as in typical S. grayi, sometimes protruded, frontal bar and all, and a thickened margin, with a very low frontal bar.

            As will be seen this sub-species, as well as S. g. gigantea, possesses some of the characters of both S. grayi and S. ritchiei but as the specimens which show intergrading links are between these two forms and B. grayi, this fact, taken in connection with the circumstances under which they are found, points clearly to the conclusion that they are derived directly from S. grayi.


            I found about fifty of this singular little Strophia clinging to the stems of two or three small trees that grew just south of the deep gorge, that limits the southward range of S. grayi, as given under that species. The space in which they occurrred could not have exceeded a hundred square feet. No specimens of S. grayi, were, however, found very near them, and this little colony had become isolated, and from some cause had advanced far toward forming a species."

Close Window