170 PHOLADID^E. 



appear that only one species exists ; but that malacologists 

 may judge, we give specific descriptions of the two phases, the 

 one being called Pholas papyracea, the other, P. lamellata. 



PHOLAS, Linnseus. 

 P. PAPYRACEA, Solander et Auct. 



P. papyracea, Brit. Moll. i. p. 123, pi. 5. f. 3, 4, 5, 6, and pi. 2. f. 1 ; 

 (animal) pi. F. f. 4. 



Animal elongated, subcylindrical ; mantle closed, except a 

 small rayed aperture for the foot, as long as one exists, and 

 which corresponds in position with a similar aperture in the 

 membrane connecting the doming of the shell, and is styled 

 by Dr. Turton a " spiracle," but which may perhaps in this 

 species, the only one of the Pholades that has it, be for the 

 purpose of a partial issue, or rather protrusion, without the 

 solution of continuity of the ventral membrane of the animal, 

 of the hyaline cylindrical appendage which exists in all 

 bivalves, to secure for it a point of support when the foot 

 becomes so much diminished as not to afford one. In all 

 other bivalves this stylet is not visible, being imbedded in the 

 body and upper part of the pedicle of the foot, which is the 

 leaning-stock or point of resistance, except in the Anomice, 

 OstrecRy and Pectinidte, in which, as the foot is reduced almost 

 to nothing, the mass of the body is the only point d'appui ; 

 but when the dome of the shell of the Pholadidea papyracea 

 is removed, the dark basal point of the stylet presents itself in 

 the centre of the mottled belly, precisely where the foot is 

 placed in the group of the Pholades ; or the fissure may be, for 

 flux and reflux of the water for branchial purposes. 



The siphonal apparatus consists of a long elastic sheath, 

 which is often protruded to double the length of the shell, 

 but in a state of half-extension it becomes highly corrugated ; 

 it is clothed with a dull red-brown epidermis, under which it 

 is bluish- white ; the margin of its terminus is finely fringed 

 with short white cirrhi ; within the sheath are the anal and 

 branchial tubes, the former with the margin quite plain, but 



