Cerion incisum Dall,1905
Typical form south side of Little Abaco, opposite Marsh Harbor, and on the opposite shore of Grand Bahama at Riding Point; variety reticulatum at the Sugar Loaves, rocks northwest of Elbow Cay, off Great Abaco; variety incisum (nearly all dead or subfossil). Stranger Cay, northwest of Little Abaco, and one specimen, apparently the same, at Sweeting's village, Little Harbor, Great Abaco; var. vermiculum at Mathews Point, south side of Great Abaco. This member of one of the most difficult groups of Cerion has been submitted to Dr. Pilsbry, who regards it as new and forming a parallel series to C. agrestinum Maynard, from New Providence. As he has recently monographed the group I have adopted his opinion. The species is named in honor of Mr. Owen Bryant, the collector.
Typical form. PI. LVIII, fig. 12.-Shell large, slender, ashy white, or white marbled and longitudinally streaked and clouded with nut brown of varied intensity; the apical 2½ whorls subtranslucent, the remaining ten opaque, smooth and somewhat polished, or more or less sculptured by fine oblique wrinkles with subequal interspaces about three to one millimeter on the line of the suture; apex beehiveshaped; remainder of the shell subcylindric, the last whorl rising a little near the aperture, the peristome thickened, somewhat reflected, rounded, simple, waxen white; throat brownish, with a short low parietal and feeble axial lamina or ridge of callus; umbilicus with a deep narrow chink; the sutures are not impressed; the immature shells are trochiform, with a narrow axial perforation, a small sharp lamina on the pillar, usually a short feeble tooth on the roof of the aperture and very rarely a faint trace of a callosity on the basal wall also, but I have noticed this only once or twice; measurements of the mutations of this species show the following as divergencies (U. S. Nat. Mus., No. 179,442) :
Surface Whorls Height Max. Diam. Type Form.
Smooth .............12.5 37.0 mm. 12mm. "
Smooth .............10.5 28.5 11.25 "
Feebly striate.....12.5 37.0 12.5 "
Sharply striate....12.0 27.0 10.0 "
Sharply striate....12.0 26.5 8.0 "
Feebly striate.......9.5 21.0 8.0 "
Subreticulate......11.0 26.0 10.0 Variety a.
Subreticulate.......9.5 21.5 10.0 " "
Very sharply striate.12.0 28.0 10.0 Variety b.
Very sharply striate..10.0 25.0 12.0 " "
Very sharply striate..11.0 22.5 11.0 " "
Very feebly striate....10.0 19.0 7.5 Variety c.
Feebly striate...........10.0 19.5 7.0 " "
Variety a (reticulatum). PI. LVIII, fig. 8.— Shell smaller, colors, tending to livid or purple below ashy white, which is arranged more or less in narrow spiral lines which cut the white wrinkles at nearly a right angle giving a very marked reticulate effect, the striation notably sharper than in the type form.U. S. Nat. Mus., No. 179,443.
Variety b (incisum). PI. LVIII, fig. I0. — Shells stouter, with still sharper sculpture, the form top-heavy, with the maximum diameter nearer the apex than to the base, a less marked umbilicus; the young with a larger axial perforation and on both the upper and lower walls of the aperture a pair of strong short low laminæ beside one on the pillar, making five in all, in the aperture of a shell with six whorls. U. S. Nat. Mus., No. 179.440.
Variety c (vermiculum). PI. LVIII, fig. 3. — Shells small, nearly smooth, slender, subfusiform, with the color in large subaxial marmorations or nebulæ. U. S. Nat. Mus., No. 179,442.
The range of variation in size; sculpture, and color, as above noted, is very large yet the various forms have nevertheless a general resemblance which points to their common origin. Large numbers of the typical form were obtained.
Dr. Pilsbry remarks of them: "a species not hitherto known, very closely related to agrestinum of New Providence, but with a general tendency to be larger, longer, more solid and varying to smooth, which agrestinum is not known to do. The umbilical slit is also ordinarily longer in your shells and the parietal lamella smaller. The suture above is also more seam-like. These forms are also related of course to marmoratum, martensi, and various other forms all more remote geographically than agrestinum. C. fordii is a stouter more coarsely sculptured species." (Dall, 1905:443-444).