Strophia curtissii Maynard, 1894

Original Description

 

"27 STROPHIA CURTISSI Novo.

Curtiss' Strophia.

Fig. 33, A, young; B, side view of type; C, front view of the same.

            DESCRIPTION.

SP. CH. Size, rather below medium. Shell, rather thick and

heavy. Striations, prasent. Animal almost wholly brown in color.

Whirls, 10. Examined 2,000 specimens.

            Form of shell, inclined to be cylindrical, the first and second

whirls being nearly equal in diameter, and the third is but little

smaller, then the shell slopes rather quickly to a quite blunt point,

forming an angle of sixty degrees. The striations are quite numerous, twenty-six on the first whirl, not very prominent, rather

irregular, and not arranged in lines; they are slightly inclined from right to left, are narrow, hence the inter­spaces are wider than the prominences. The striations are not furrowed, but are rounded and smooth.

            Aperture, rather small, but measures a little more just within

than at the entrance. Lower tooth, not very prominent, .05 high by .10 long, and its position is about cen­tral; the upper is absent, being

represented by a slight protuber­ance.

            Margin, not produced forward as far as the diameter of the shell, and is very slightly inclined to the right, but not beyond the side; it is not thickened, measuring .04, but the outer posterior portion is produced backward into a sharpened edge, but which is not rolled downward. The frontal bar is quite distinct, and the striations are completely interrupted by it, never appearing within.

            Color of shell externally, white, prominently and plentifully

flecked with reddish brown of varying shades; internally, purplish

brown, fading into yellowish white on the teeth and margin of the

aperture and tooth. Apex, pale horn color.

DIMENSIONS.

Size of type, .98 by .40. Largest specimen, 1.23 by .42; smallest,

.87 by .36; greatest diameter, .45; smallest, .35. Longest specimen,

1.25; shortest, .78.

OBSERVATIONS.

Individual variation from the typical locality is not great. There

is a tendency to vary somewhat in fleckings, some specimens being more heavily marked than in the type and others less heavily. There are, however, three prominent departures from the type, which if placed under different environment at any time, will form distinct species, but which intergrade so completely with the type form that I have not considered it necessary to name them, but have designated them by numbers. The type form occurs in the large cemetery to the eastward of Nassau, on the western side of a path which crosses the grounds.

            No. 1. Form of shell about that of the type, but this is a rather small form, .90 by .40, with a thicker margin, (.10), projecting more forward, smaller aperture, more striations, 31 on the first whirl, with the interspaces about as wide as the prominences. The fleckings are slight and much paler within than in the type, with no distinct blotchings. This form is inclined to occur to the westward of the

type location.

            No.2. An elongated cylindrical form, with eleven whirls, the first three of which are about equal in diameter, and with the remainder forming a rather acute point, having an angle of 50 degrees. The striations are fewer than in the type, 21 to the first whirl, less prominent, but with lines of growth between. The margin is thick (.07) with aperture widening from within. The fleckings .are inclined to mass into blotches, but their color is pale. This form occurs to the southward of the type location.

            No.3. Of about the same form as the type, but is a larger shell, 1.10 by .45, with a very thin margin, about .03, and apertures

widening from within, striations 27 to the first whirl, very regular, but not in lines. Occurs to the extreme southward and eastward of the type location.

            No.4. Is a more pointed form than the type, narrowing from the first whirl. About the size of the type, with margin and aperture similar, but the striations, excepting on beginning of upper whirl, near margin, are reduced to irregular lines of growth, which are promi­nent only in places, leaving the shell quite smooth and polished in spots. The fleckings are massed in blotches and are very dark in color, contrasting with the creamy surface. This form is very rare. I found five only among some banyan trees that stand on the top of a little hill in the cemetery, near an old ruin.

            No.5. Rather singularly there is a form of S. curtissii on Spotter's Key, a little islet lying in the middle of Nassau harbor, distant from the cemetery about a third of a mile. This islet was

formerly fortified, as the remains of old ramparts testify, and although now it is seldom visited, there must have been constant communication between it and the main island in former times. It was then doubtless that Strophia curtissii was introduced. Since then it has changed considerably. In fact, it has become one of the most interesting forms of the genus that I have seen. The form and color does not differ exceedingly from those of the type, but the size is somewhat smaller (.87 by .40). The margin is pushed forward almost to the outer diameter of the shell (in some specimens beyond this), and has become very thin. But the most important feature is the tooth, which is at least three times as long as high. (See Fig. 34 a, where I give a cut of this tooth, side and top view, and compare with ib. b, where is given a view of the type, S. curtissii). The striations are quite regular and arranged in lines.

            Were it not for the fact that not every specimen on Spotter's Key has the tooth elongated to the extent shown in the type, I should not hesitate to consider this well-marked form as a species. I have elsewhere shown that on wind-swept islands, like the Caymans, species of Strophia have elongated teeth, in order that the animal may have better control over its shell, as it has no muscular attachment to it ; and here on this little key, lying as it does in the middle of the harbor, the form I have just described, has, through the progress of evolution, acquired a similar tooth to those which characterize the Cayman Strophias.

            Young specimens of Strophia. curtissii have the central tooth missing, but with the upper well developed. There are, however, no other teeth whatever, as is usual in some other species.

            Known from the closely-allied S. thorndikei by the larger size, less creamy color and thicker margin to the aperture.

            From other of the short-toothed Strophias which occur on New Providence and in its vicinity, in which the central tooth is only twice as long as high, this species may be distinguished by the fleckings, combined with usual absence of the upper tooth. Occasionally this is present, but is then very minute but oftener the prominence glven in the type is not even seen.

            I have named this beautiful Strophia for my friend Mr. George F. Curtiss, to whom I am not only indebted for many acts of kindness when he was with me, but also for ready sympathy and encouragement in all my pursuits.

            This common Strophia has found its way into collections under the name of S. zebra of Reeve, but this is not the S. zebra described by him and figured by him in his monograph. The true S. zebra is a shell without striations, but with lines of growth only, and with the markings massed together in large, prominent blotches. My friend, Mr. F. C. Browne, has some Strophias in his collection, labelled as coming from the west coast of Andros, which answer to Reeve's figures and description of S. zebra quite nicely. Unfortunately Reeve says his S. zebra came from the Bahamas, without giving direct locality.

HABITS AND DISTRIBUTION.

The first specimen of S. curtissii, that I ever saw was gathered by Mr. Curtiss from some bushes which grew near the western border of the pond that lies to the eastward of the city of Nassau and which is known as Waterloo. Here they are scattering and are mostly confined to the south side of the road which goes out to the beach near the old magazine, but I found a few dead shells west of this road.

            Later we found the type locality, which was in the cemetery between Waterloo and the city. On the north side of this enclosure is the type locality. On the hill in the middle of the cemetery among the fig trees I found a sub-species (S. c. nivea) and to the eastward of a path crossing the cemetery, another species, S. thorndikei. On the hill was also the smooth form, No.4, and in the valley beyond it a

similar form to that found at Waterloo (No.2) already described. Outside the cemetery wall to the westward I found a few, also large, coarsely-striated specimens. I could not trace them south of the southern wall of the cemetery, nor even quite to the wall. They are

exceedingly abundant in the type locality, which occupied about a quarter of an acre. Here the bushes, to which they had evidently been clinging, had been cut down, and many of the shells were upon the herbage. In other places, especially toward Waterloo, they were clinging to shubbery; all were hybernating when we found them early in March, and they were often gathered together in clusters. When taken into the house they began to move about, after a time, but in most cases refixed themseves either to one another or to the sides of the boxes, in which they were kept.

            The elongated form, No 3, occurs between the type locality south and the top of the hill and a little beyond it. Numbers 1, 2, and 3, are about equally common, each representing about one per cent. of the type form, but No.4 is very rare, only five being taken.

            I liberated a number of these Strophias in the yard in which we lived, on the corner of Bay Street and Kemp's Road, in order to see if they would survive, as a species, under different environment, and fully intended to have taken a lot to U Key, but failed to do so as we did not visit this key a second time.

            Mr. Curtiss made an interesting discovery regarding the form which inhabits Spotter's Key, as he found three pairs which were on the ground clinging together for mutual fertilization. This was on March 27th, directly after rain."

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