The River Snails - Family Streptomatidae

Habitat.— Tennessee.

Sub-Genus PLEUROCERA, Raf.

Shell elongated, conical, regular; aperture with short canal; columella without callus. Tryon describes eighty-two species.

The Ponderous Pleurocera (A. ponderosa, Say) is a heavy cone of flat coils, the last one keeled. The short lip canal turns to the left. The surface is olive, the lining white. Length, 2 inches.

Habitat.— Tennessee.

A. undulata,

Say, has a handsome elevated spire of broad flat coils that cover a row of knobs, and so produce wavy folds below the deep suture. The white lip projects. Length, 1 inches.

Habitat.— Ohio River.

A.

canaliculata, Say, is distinguished by its distinct groove on the body whorl. Variable in form and size and ranging in colour from pale green or yellow to black, yet it is distinct. It is very common at the falls. Length, I inch.

Habitat.— Ohio River.

Genus GONIOBASIS, Lea Shell heavy, ovate or elongated; aperture angled in front, but without canal or notch. A large genus of one hundred and fifty species, one-half of the entire family, distributed east of 188 The River Snails the Mississippi, but well represented (as is no other genus) on the Pacific slope of the Rocky Mountains.

The collector must search for these snails in the clear water of creeks that flow down mountain slopes. The green alga are their accustomed food.

The Virginian Goniobasis (G. Virginica, Gmel.) is slender

and long, with about six whorls, rounded a little, and banded with red near the middle and base of each. Some forms are finely ridged throughout, with ten or twenty lines on the body whorl. The tip is always worn off. The colour is dark brown or olivaceous. Length, i to 1 inches.

Habitat.— Delaware and Schuylkill rivers.

The Plaited River Shell (G. plicilera, Lea) has keen edged folds crossing the whorls to the very apex of its horn-like spire. But for its dark complexion this river shell might be mistaken for one of the ladder shells, though the latter are marine mollusks and decidedly pale. Length, I inch.

Habitat.— Oregon.

The Sharp-Lined River Shell (G. acutifilosa, Strns.) bears a double row of sharp tubercles winding up its tall spire, and below these, on the body whorl are four or five plain, sharp keels that very prettily crimp the thin outer lip. The tip is usually missing, else the shell would be over an inch long.

Habitat.— Eagle Lake, Cal.

G. rubiginosa,

Lea, is rusty, with spiral keels on all but the smooth body whorl.

Habitat.—Oregon.

G. nigrina,

Lea, is black, has smooth, rounded whorls, and is slender. Length, about f inch.

Habitat.— Tributaries of the Sacramento River.

G. bulbosa,

Gld., smooth, and swollen, lives in streams that feed the Columbia River.

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