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The Pyramid Snails

Genus PYRAMIDULA, Fitz. (PATULA of recent authors)

Shell cone-shaped to flat disk-shaped, with open umbilicus; opaque, one-coloured, banded or flame-streaked; whorls rounded or keeled; aperture rounded; lip thin, simple. Foot undivided, lateral margin with a border set off by a groove. No mucus foot pore; eye peduncles long and slender.

Dull coloured, ground-living snails, found all over northern temperate land areas.

The type, P. ruspestris, Drap., is a neat, low-coned, brown snail with rounded coils and a deep pit. Diameter, 1/2 inch.

Habitat.--Central and Southern Europe.

The Perspective Pyramid (P. perspectiva, Say) shows a widening pit separating its flattened coils. The reddish streaked, horny shell is finely striated. Animal has narrow white foot; head dusky, blue, granulated; eye-stalks slender. Diameter, 3/4 inch.

Habitat.-Northern United States.

Sub-Genus PATULA, Held

Shell depressed, top-shaped, with a deep, conical umbilicus; foot large. A sub-genus of several hundred species; of universal distribution.

In the eastern states these snails lay eggs; the western species bring forth young alive, probably because of the aridity of the climate; eggs laid in the ground would not hatch, owing to drought.

P. alternata in the East and P. strigosa in the Rocky Mountain region, are among our commonest land snails.

The Alternate Patula (P. alternata, Say) is decorated with interrupted streaks of reddish brown, that often zigzag across the whorls. The shells are thin and transparent, sculptured with close diagonal raised striae. Lip smooth. Found in colonies on decaying logs or in other damp places in woods, or even in city backyards. In winter they are found in pockets. Binney believes this crowding together is for the purpose of preserving bodily warmth. Diameter, 1 inch.

Habitat.-Eastern and central United States.

In P. solitaria, Jay, the large body whorl is banded with three brown lines. It has a deep narrow pit, and a somewhat elevated apex. Habit, solitary. Diameter, 1 1/2 inches.

Habitat.-Central and northwestern states.

The Streaked or Mountain Snail (P. strigosa, Gld.) is streaked by two brown bands that encircle the body whorl, the upper one of which winds almost to the apex. In contrast to the translucent flesh tint, a band of opaque white separates the two brown ones. The best place to look for specimens is at the foot of crumbling limestone cliffs.

This is the commonest snail between the Rockies and the Sierra Nevada. In Utah and Idaho it is especially abundant. Varieties reach the altitude of 8,500 feet. Naturally the species is variable. Diameter, under 1 inch.

Habitat.-Rocky Mountains, western slopes.

P. Cumberlandiana, Lea, has the open pit and the flattened spire of this sub-genus. It reminds us of the marine genus Solarium, the sun-dial shells. Finely cut, erect ridges diagonally cross its whorls. A thin-edged keel divides the body whorl into an upper and a lower half, and notches the outer lip. The markings of brown are like those of H. alternata. Diameter, 3/4 inch.

Habitat.-Cumberland Mountains, Tennessee.

Genus GLYPTOSTOMA, Bland and Binney

Shell discoidal, with slightly elevated spire; whorls rounded, six; lip thin, simple; umbilicus broad, showing all the coils plainly; colour black or reddish brown; parietal wall of aperture beautifully sculptured. Animal bluish slaty.

The single species known, G. Newberryanum, Binney, is a large snail very common on rocky hill slopes about San Diego, Cal. In summer it hibernates, with its aperture closed. The characteristic spiral sculpture of the parietal wall of the aperture becomes overlaid by a white callus as the shell matures. So the trait upon which the generic name is based is seen only in immature specimens. Diameter, 1 to 2 inches.

Habitat.-Southern California.

Genus POLYMITA, Beck

Shell flattened, globular, brilliantly coloured, solid though thin, whorls three to five; axis solid, outer lip not expanded; animal black above, slaty below.

The Painted Snail (P. picta, Born.), one of the most gaily dressed of land snails, lives in trees. Individuals are quite different in colouring; this accounts for the large number of named varieties. The ground colour has its beauty heightened by narrow stripes of darker, contrasting colours, that outline the sutures and the outer lip. There are yellow shells ornamented with a scarlet spiral thread; chestnut brown with white bands; dark blue with white-edged black bands, and salmon red, similarly trimmed. The large, half-moon shaped aperture shows a violet or white interior. The simple lip is thickened within.

What a sight to see these gay little mollusks slipping about among the tree branches which are their homes! They harmonise with the brilliant tropical vegetation. Diameter, 1 inch.

Habitat.-Cuba.

Genus SAGDA, Beck

The Tied Helix (H. alligans, Ads.), is thimble-shaped, with a concave, depressed base and blunt apex. Whorls eight to ten, flattened, the last one faintly keeled. The lines of growth show as faint, diagonal striae. The white shells are invested with a yellowish horny epidermis. The aperture is semi-lunar; lip thin, sharp. Umbilicus wanting. Height and width, 1 inch.