MOLLUSCA. 685 ium, with an eye at the external base. The anus is situ ated at the branchial indentation on the left side. The penis is situated on the right side of the neck. It is external, with a crooked blunt lateral process near its extremity.
The mouth is in the form of a short proboscis. The tongue is armed with spines, and is long and spirally folded. The salivary glands are large. The stomach is membranaceous, giving off the intestine near the car dia. The intestine makes two folds. The liver, with the testicle in the male, and the ovarium in the female, occupy the posterior part of the body, under the spire of the shell. Two species are natives of Britain.
I. Sigaretus haliotoidea.—The tentacula in this spe cies are short and flat, and the foot rounded behind. It is figured imperfectly by Montagu in Testacea Briton nica, vignette 2. fig. 6. It occurs frequently on various parts of the coast.
2. Sigaretus tentaculatus.—The tentacula are produc ed and filiform. The foot pointed behind. This species was discovered by Montagu at Kingsbridge, Devon vonshire, in 1809, and described and figured by him in Linn. Trans. vol. xi. p. 186. tab. xii. fig. 5 and 6.
The animals of this order were formerly valuable in an economical point of view. Many of them yield a rich dye, which was much sought after by the ancients. This was chiefly extracted from the animal of the Murex Brandaris, and was termed Purpura. But it is likewise furnished by the animals of Purpura lapillus, Scalaria clathrus, and Planorbis corneus. Since the introduction into Europe of the Cochineal insect, the use of this dye has been superseded, so that we are now in a great mea sure ignorant of the process which the ancients employ ed to extract it.
The Pectinibranchim, although no longer sought after as furnishing colour for enriching dress, are still in esti maticn as articles of food. The Periwinkle is frequently gathered by children in this country, as well as the Ne rita littoralis, and eaten when boiled. The welk and buckle are likewise sought after. All these animals arc extensively employed as baits for catching fish.