The Staircase Shells - Ladder Shells - Wentletraps - Family Scaliidae

THE STAIRCASE SHELLS - LADDER SHELLS - WENTLETRAPS - FAMILY SCALIIDAE.

Shell

white, polished, turreted; whorls sometimes uncoiled, with longitudinal ribs bearing prominent plates; aperture round; operculum spiral, horny. Head has retractile proboscis; tenta cles close together, with eyes at their bases; jaws toothed or spiny; radula elaborate. Sexes distinct. A creeping, carnivorous family of world-wide distribution, allied to Ianthinidx.

Genus SCALA, Humph.

Characters of the family. Living species, 200; fossil species, 200.

The peculiar flanges that decorate these shells, making them resemble spiral staircases, are the successive limits of periods of growth. Each in turn has been the shell's lip until growth began again, and it was left behind. The genus has a wide distribution from arctic to tropical seas in eastern and western hemispheres, from low water mark to abyssmal depths. The West Indies have furnished the greatest number of species. Large species measure 21 inches in length; one species, 4 to 5 inches. When' disturbed, the wentletraps exude a purplish fluid.

The Precious Wentletrap (S. pretiosa, Lam.) has had a romantic history. It was long considered a Chinese shell, but was later found also off the Australian coast and among the Moluccas. It is one of the largest known species, reaching 24 inches in length. It has a broad-based spire of eight roundish whorls, smooth and white, decorated with ivory white flanges or ribs that cross the whorls at regular intervals. The sutures are deep and the umbilicus wide. The mantle has a flaring rim.

About the year 1700 these shells attained an exorbitant and fictitious value in the estimation of shell collectors. Forty guineas ($200) was paid for a single specimen. Fifty years later this price 157 The Staircase Shells. Ladder Shells. Wentletraps was cut in two. The clever Chinese counterfeited the precious shells, too rare for their liking, by moulding them from a paste made of rice flour. Now the range of the species is found to be much less restricted than was supposed in the eighteenth century. A good specimen of S. pretiosa can be had of almost any curio dealer for a dollar or two.

The Ladder Shell (S. Crrcenlandica, Chemn.), Greenland to Massachuetts Bay, has been found abundantly in the stomachs of fishes taken on the Grand Banks and farther south. The shells are picked up on Nahant beach and on the Maine coast. They are

graceful, turreted, heavy, with sharp spire of ten whorls, flattened, close-set, each bearing revolving ridges and crossed by oblique, prominent white ribs. The ground colour is brown or bluish. A rib, angled at the inner point, edges the round aperture.

The animal is yellowish gray, splotched with white. The foot is squarish and thick. The head is rounded above, elongated, with a shiny black eye at the base of each short tentacle. The large mouth eagerly seizes bits of fresh beef, when the mollusk is in an aquarium. Its movements are sluggish. Length, 1 inch.

S.

lineata, Say, found from New England to Florida, is a thick little ladder shell ornamented with two brown spiral bands on the body whorl. The shell is elongated, with six or seven whorls, and regular cross ribs throughout its length. Length, about inch.

S. angulata,

Say, with its ribs a bit angled next to the suture above, has six to ten whorls which do not touch each other in the coil. It is about inch long, rather stout and white. It occurs from Connecticut to Florida and Texas.

S. multistriata,

Say, of our Atlantic coast, is known by the multitude of its ribs that crowd closer than in any other species. It is a solid white shell of graceful form. Length, to 4 inch.

S. clathratula,

Ads., found on European coasts, and from New England to Cape Hatteras, is a polished white, almost trans parent shell, slender and graceful, about inch long. Its rounded whorls bear a great number of cross ridges.

On the west coast is found S. Hindsii, Cpr., a delicate white ladder shell, scarcely an inch long, with a needle point and rounded whorl crossed by many thin, sharp ridges. Professor Keep says these shells are mounted for ear drops, sometimes, by enterprising jewellers. Southern California.

The Staircase Shells. Ladder Shells. Wentletraps S. Indiorum, Cpr., is found on the California coast and north to Vancouver Island. It is thin and white, an inch long, with numerous cross ribs on its ten whorls. Occasionally it is found in a variety, tincta, tinged brownish purple, in Southern Califor nia.

S. mirifica, a rare deep water species, I mention here because it is unique. It has the distinction of being the most highly coloured of all deep sea mollusks. As a rule abyssmal shells are dull and colourless. This notable exception is white, tinted with bright rose-colour.

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