BYSSOMYA, a genus of Conchiferous Mollusks, separated by Cuvier and placed by hint under his Acephalons Testacea, between Pandora . and Iliatella. De Blainville, who approves of Curier's separation, observing that, though the shell differs little from Saxicava, the animal is very distinct, arranges it in his family of Pyloridea, between Saxis care and Rhomboides.
Generic Character.----Animal more or less elongated, subcylindrical, elongated behind by a long 'tube, which is bifurcated at its extremity only. A hole at the lower and anterior part of the mantle for the passage of a small conical canaliculated foot, and of a byssus situated at its posterior base. Two strong adductor muscles.
Shell often irregular, covered with a strong epidermis, oblong, strongly striated longitudinally, equivalve, very inequilateral, obtuse and wider before, awl attenuated or rostrated as it were behind. Umbones but little developed, though distinct and a little curved forward. Hinge toothless, or only having a rudiment of teeth under the corse let. External ligament ra ther long. Two strong, distant, and rounded muscular im pressions.
Example, Bye sontya pholadia, Sasicara photo , dis of Lamarck.
The species inhabits the northern seas, living in the fissures of rock* in company with Ate i/ i (Mussels), and attached by its byssus ; but sometimes it buries itself in the sand or lodges in small stones, the roots of Foci, and even iu the polymorphous illepora : in the latter cas3, according to 0. Fabricius, it is without byssus.
Forbes and Hanley, in the 'History of British Molluscs,' refer 13. pholadia of Bowdich and the S. pholad id of Lamarck as synonymous to Saxieara rwfwa. [SAXICArls llYSSUS, the name of a long, tielicate, lustrous, and silky fascieulus of filaments, by which some of the eonchiferous mollusks (the 346 /sera, Mussels, and Malleacea, Hammer Oysters, for example) are moored to submarine rocks, &c. This is not, as some authors have stated, a secretion spun by the animal, but, according to Dc Blaiuville, an assemblage of muscular fibres dried up in one part of their extent, still contractile and in a living state at their origin, a condition which they enjoyed throughout their whole length at the period of their attachmcut. The tendinous foot of Byasoarea and Tridaena seems to be a step towards the organisation of a true byssus. In the great Piano of the Mediterranean this substance is well and largely deve loped, and its situation is in a fleshy sac or sheath at the base of the foot, which is attached towards the middle of the abdominal mass of the animal. In Italy the byssus is manufactured into various articles; and there are few museums without a glove or a stocking woven out of this substance. In the Great Exhibition of 1851 a large number of articles were exhibited manufactured from this substance, as well as specimens of the silk for making up.