Habitat. Philippines.
The large species were commercially important in the earliest times because they yielded more of the precious dye than the smaller kinds.
The Rock Purple or Dog Winkle (P. lapillus, Linn.) is one of the best known inhabitants of northern rocky coasts on both sides of the Atlantic. P. saxicola, Val., of the west coast, is probably the same. This species has attained its remarkable geographical range by variations which adapt it to changed conditions of life.
The collection of P. lapillus made by Cooke in Great Britain alone exhibits nineteen distinct forms. Large size, prolonged spire and small mouth characterise those found on protected coasts where food is plenty and attachment to the rocks an easy matter. A low spire, a large mouth, small size and a thick shell belong to forms taken in exposed situations where food is scarce. The most strikingly banded and brightly coloured shells are found on veined and coloured rocks, the dullest in estuaries and sheltered bays.
Linnmus called this species by a name which means "pebble": doubtless he saw, as they lay exposed by low tide, the resemblance of these numerous shells to the pebbles on the beach, and saw in that resemblance a reason for the success of the species in the struggle for existence. They share with pebbles the hard knocks all shore-dwelling mollusks get when the sea is rough. The American forms are rarely over an inch long. In England they range upward to two inches, and over, in favourable situations.
The colouring varies from whitish through all the yellows and browns, bright and dingy, to dark red. The surface may be smooth or finely cancellated or beset with tubercles. The roughest specimens in Dr. Cooke's series came from the oyster beds, six fathoms deep.
The activities of this purple are well known. He shambles about clumsily, or sits faithfully plying his drill. He is cordially hated by fellow pensioners on the bounty of the sea. He eats oysters and mussels, thrusting the long proboscis into the hole laboriously drilled through one of the valves, and sucking out the contents. Mytilis edulis, the edible mussel, is his 'favourite food. Lacking this delicacy, he will bore the shells of limpets and barnacles even pick the bones of dead fish and crabs.
44 The Purples. Dog Winkles He is almost always eating, or in quest of food; if at rest on a rock you may believe he is digesting a full meal.
The starfish, also a lover of oysters, sometimes falls upon his molluscan rival. By stealth he gathers several purples in his five fingers, laying hold of them with the delicate suckers, and bringing them to the central mouth. The stomach turned wrong side out envelops the purples which are dissolved out of their shells by the strong digestive fluids the stomach walls secrete. Hermit crabs, secure in borrowed tenements, sometimes attack and destroy a colony of purples by a concerted attack.
The egg capsules of this species are like delicate pink grains of rice set on tiny stalks. They are found in groups on protected rock surfaces. "A single individual has been observed to produce 245 capsules." Cooke. Each contains twenty to forty em bryos. The active period of breeding is from January to April, on English coasts, but egg-laying goes on all the year round. The capsules are called "sea cups." "Horse Winkle" is the Irish name for this purple "Dog Winkle" and "Sting Winkle" are English nicknames.
The original home of this species may have been northern Europe. Here it attains its maximum size. It migrated to America by way of Iceland and Newfoundland, no doubt, and down the Atlantic coast to Florida. Our forms are smaller and duller than the European.
The operculum of P. lapillus and other small univalves is the "eye stone," kept by druggists. A cinder in the eye, or par ticles of dust, adhere to the surface of the eye stone as the muscles move it about under the eyelid. Similarly, a flax seed removes irritating particles.
Thrown in a dish of water with a dash of muriatic acid these little calcareous bodies move about as if alive. The energy they exhibit is chemical, of course, but ignorant people "tell fortunes" by the aid of these animated objects.
The Florida Purple (P. Floridan, Conr.) has an elevated spire of angled whorls with fine nodules around the shoulders, it is spirally grooved and banded with yellow and black and longitudinally cross-banded with black. Lip and columella are orange; aperture paler, often banded. Canal somewhat long. Length, 11 to 2 inches.
Habitat. North Carolina to Florida.
45 The Purples. Dog Winkles The Rock Purple (P. saxicola, Val.) is as abundant on the California coast as its near relative, P. lapillus, is on the coast of New England. It exhibits as great a tendency to vary. The shell is thicker, with a smaller aperture. Specimens reach one and a half inches in length, but the average specimen is less than an inch long. The dingy exterior is marked with double spiral bands of brown. The lip is sharp; the columella twisted and flattened; the spire short.
Habitat. California.
The Grooved Purple (P. lima, Mart.) lives in deeper water, so is more rare than the last species. It has an elevated spire of four rounded whorls separated by deep sutures. Fifteen spiral grooves sculpture the surface uniformly. Colour, light brown. Length, to I inch.
Habitat. California.
The Wrinkled Purple (P. crispata, Chemn.) ranges north ward from San Francisco Bay to Alaska. The species improves as it moves to higher latitudes. Specimens from Puget Sound are two inches long, with longitudinal frills and spirally banded with rich brown. Smoother specimens, of duller hue and smaller size occur southward. The white aperture is smaller; the lip is toothed within.