"35 STROPHIA CORYI Novo.
Cory's Strophia.
FIG. 39, A, front view, B, side view of type.
DESCRIPTION.
SP. CH. Size, medium. Shell, quite heavy. Striations, present. Whirls, ten. Examined, 2,000 specimens.
Form of shel1, quite cylindrical, the first three whirls being about equal in diameter, the fourth is but little smaller, then the shell slopes to a rather blunt point, forming an angle of fifty-five degrees. The striations are not numerous, nineteen to the first whirl; they are not prominent, very regular, not furrowed, but rounded, narrow, are about half as wide as the interspaces between them, but are not arranged in lines, and very slightly inclined from right to left.
Aperture, quite small and rather contracted. Lower tooth, quite prominent, about .04 high, and about twice as long as high, nearly central in position, a little elevated, and set back about once its length. The upper tooth is about half as high as the central, is placed low, being but little above the top of the lower tooth.
Margin, produced forward as far as the diameter of the shell, is slightly inclined to the right, a trifle beyond the diameter of the shell. It is considerably thickened (.07), with the edge projected backward, and shapened, but not rolled downward. The frontal bar is quite well developed, and interrupts the striations, which are, however, slightly indicated within it.
Color of shell, externally, deep ashy brown, with the striations creamy white; internally, also brown, a little paler than on the outer surface, becoming creamy white on the tooth, margin and frontal bar.
DIMENSIONS.
Size of type, 1.00 by .40. Largest specimen, 1.12 by .42; smallest, .62 by .36. Greatest diameter, .45; smallest, 36. Largest specimen, 1.12; shortest, .62.
OBSERVATIONS.
The type form is very abundant, proportionately, and there is comparatively little variation that can be considered as purely individual. What little there is consists in a thinner or thicker margin, and slightly finer or coarser striations, but there are five distinct forms developed, which are as follows:
No.1 is an elongated cylindrical form with the first four whirls equal in diameter, and a thinner margin. This form grades directly toward S. cinerea, and I have three specimens that are direct reversions toward that species. Size, 1.10 by 1.36.
No.2. This is a singular form, nearly pure white in color, shorter, with nine whirls only, faintly yellowish within, and slightly tinted with brownish between the striations. Size, .97 by .47. This form recalls the white No.3, which has been evolved from S. cinerea.
No. 3 is a form with more numerous striations, twenty-four to the first whirl, and they are finer, the shell is darker, with dark umber blotches, which often cross the striations.
No.4. A short form, with nine whirls, and, excepting this, is a miniature of the type. Size, .70 by .86.
No.5. The smallest of all, with a very thin margin and with numerous striations, 30 to the first whirl, and the color, without and within, is much paler than in the type. Size, .65 by .37.
This last form is almost sub-specific, but there still remain too many specimens having intermediate characters, that bind them to other forms, to so consider it.
Form No.1 is very rare, less than one per cent. of the whole. No.2 is more common, about .10 per cent. of the whole. No.3 is less common, about 1 per cent.; while Nos. 4 and 5 are more abundant, and form about five per cent of the whole.
Cory's Strophia may be known by the heavy shell, thick margin, and peculiar brown color, with the contrasting creamy white striations.
I have named this species for Mr. Charles B. Cory, the well known ornithologist, who has exhibited considerable interest in West Indian shells, especially in the genus Strophia.
HABITS AND DISTRIBUTlON.
Cory's Strophia is an abundant species on the extreme west end of New Providence, and is found clinging to bushes and herbage that grow along the bay. I traced it northward as far as the open grounds which lie about the single house that stands on this bay, and southward as far as the bushes extend, and eastward to the pine woods.
In regard to the locality occupied by the forms, I cannot speak with certainty, as I did not collect all of the specimens which were procured. and, in fact, had a few hours only in which to examine the locality, as we came to anchor in the bay for a short time, when we were bound for Andros.
One of the most singular things that I have to state regarding this Strophia, is the fact that I found five undoubted specimens on Spruce Key. Two of these only were living, all the rest were dead. Thus on this little key, which is only a few hundred yards long, live two species of Strophia.
We have seen that even among typical Strophia cinerea there is aninclination to evolve a white form (No.3) and that this is quite like form No.2, which is evolved by S. coryi. We also find that through form No.1 of S. coryi, there is a decided tendency to a reversion towards S. cinerea, in fact, I have two specimens which are nearly or quite typical S. cinerea. I do not hesitate to affirm with these facts in view, showing so clearly the relationship of the two species, that S. coryi, as found on the west end of New Providence, is derived from S. cinerea. Now comes the question as to where the specimens of S. coryi which I found on Spruce Key came from. Has S. cinerea evolved two colonies of S. coryi, one for Spruce Key and one for the west end of New Providence?
The presence of a species of Strophia evolved from S. cinerea on the west end of Now Providence is accounted for by supposing, quite reasonably, that the parent stock was transported there by the persons who settled on the plantation which is now there, the house of which I have spoken as being near the colony of Strophia coryi.
Now in regard to the specimens of S. coryi, found on Spruce Key, it seems more reasonable to suppose, that they also were evolved directly from the parent stock of S. cinerea, possibly through form No. 3, than to suppose that they were transported from the west end of New Providence, some twenty miles away. The shells from Hog Island could have reached Spruce Key through the agency of ocean currents, as will be seen by consulting the diagrammatic chart given in fig. 40.
The scale of this chart is, roughly estimated, about two inches to the mile. A, is Hog Island, e, Middle Bay, the home of typical S. cinerea, C, is Spruce Key, but as the tide sets east and west through Nassau Harbor, in the ebb and flood, and north and south through the Narrows, N, between Hog Island and Long Island, B, a shell falling into the water at c, would quite possibly reach Spruce Key on the ebb tide.
In order that the reader may more fully comprehend the localities inhabited by the interesting species, sub-species and forms of Strophia, in the immediate neighborhood of Hog Island, I give the accompanying diagrammatic chart.
E. is a portion of New Providence, east of Spotter's Key. A, is the cemetery, and the locality bordered by the dotted lines, shows the range of S. curtissii, extending as far east as Waterloo, b. In the midst of these bounds, and in the cemetery, is the limited range of S. thorndikei, t.
Leaving the main island of New Providence we cross to Spotter's Key, the eastern end of which is shown at D. This is the home of the long-toothed form of S. curtissii (No.4).
Crossing another narrow channel, further north, we come to Hog Island, and at e, is Middle Bay, before mentioned, with S. cinerea, living along its border, a widely different species from those which are found on the east end of New Providence.
Crossing the hill back of the bay, then a swampy valley, we ascend the hills which form the beach ridge and come to the scattered colony of S. c. robusta, f.
To the eastward on the southern side of the point of the island is the restricted colony of S. c. tracta, g.
Crossing the Narrows, N, which are about one fourth of a mile wide, we find the western end of Long Island, B.
[ I will here remark, that, probably owing to the great extent of the Bahamas, the names of some small keys are applied to more than one island. For example, we have this name "Long" applied to no less than three different keys: one near New Providence, as now given, one near Rum Key, and one in the Crooked Island Passage, further south.]
The buildings of the hospital occupy the western end of Long Island, and to the north of them is a little bay, k, east of this bay, around the point, the colony of S. c. mutata begins, and extends to a sand-beach, midway of the key at l, thus in the chart the western half only of Long Island is given. North of the western end of Long Island is the little rocky islet known as Spruce Key, on which two distinct species of Strophia live, or did live at the time of my visit, March 29th, 1893, namely, S. albea and S. coryi (see c).
At F, directly north of Hog Island, is the desolate Salt Key, which I have not yet visited, and so cannot say whether it contains any species of Strophia or not.
It is still too early in the course of my investigations to even speculate intelligently as to the probable origin, time of distribution, etc., of the various forms of Strophia found in this locality, but this chart will, I trust, prove of interest in showing the direct localities in which the mollusks of which we are treating occur.
As an interesting item in the habits of S. coryi, I have to add that since the last sentence regarding that species was written one of the type specimens contained in a box on my table has left his fellows, crawled up the sides of the box about an inch and a half, and fixed itself there. Now this specimen was taken on the west end of New Providence on April 17th, 1893, and last night, that of December 14th, 1894, it has shown signs of life. This shell has, during these twenty months, been kept in a box, with others, and although some showed signs of life during the summer of 1893, they have, so far as I have observed, all remained quiet up to this time. Of course they have been kept in a warm room and in the drawer of a cabinet, where they have been but little disturbed. This incident is very instructive as showing the great length of time in which at least individuals, of this group of animals can live under adverse circumstances. See further remarks on this head under Strophia grayi and S. ritchiei."
