BIVALVES. 



PLATE LIX. 



Genus. SPONDYLUS. 



Character. Shell shaped like an ear, underneath rough, and covered with spines; 



two teeth bent backwards, with an intermediate hollow space. 



Species. 



No. 1. Spondylus imbricatus. Shell of an olive green, rough, and invested with 

 folds and ridges like the tiles of a house, and having a few spines near the 

 hinge. From a specimen in the Author's Museum. 



No. 2. Spondylus spinosus. Shell of a pale red, streaked circularly with dark 

 red ; the spines very numerous and blunted at the ends, projecting far out, 

 and covering the whole surface. This shell is found in the East Indies, 

 and though very rough in its external form, is nevertheless elegant in its 

 appearance. From a specimen in Mr. Bullock's Museum. 



No. 3. Spondylus digitatus. Shell of pale pink colour, invested with white 

 ribs, digitated, or shaped in the manner of fingers. This shell is supposed 

 to be very rare, and is of a curious and singular shape. From a shell in 

 the Museum of Mr. Hankinson. 



Genus. CHAM A. 

 Character. Shell thickened ; hinge strong, placed in a crooked opening. 



No. 1. Chama lazarus. Shell imbricated and spinous, with very deep ridges 

 inserted longitudinally. Linnaeus, with his usual want of delicacy, has 

 named it Lazarus, from its resemblance to a sore, infested with proud 

 flesh, a denomination certainly more ingenious than agreeable. It is a 

 native of the East Indies. 



No. 2. Chama circularis. Shell of a pale red colour, invested with spines, 

 pointed and depressed. This shell is rare, and a native of the South Seas. 

 From a specimen in the Museum of Dr. Lettsom. 



No. 3. Chama costata. Shell of a pale red colour, the edges fluted and decus- 

 sated. From a shell in the Author's Museum. Native place unknown. 



REMARKS. 



The genera Spondylus and Chama have, in general, a considerable external resemblance, 

 the difference consisting almost entirely in the character of the hinge. The forms of the 

 upper and under shell of each of these species, differ very much from each other ; some- 

 times the lower shell is much larger, and receives the upper one in the manner of a cradle 

 or nest. This is also the case with some of the rarer species of Pectens, to which shell the 

 Spondylus has an analogy, having a small kind of wing placed near the hinge, and only 

 upon the lower shell. These shells are found chiefly in the warmer climates of the globe, 

 and form a numerous assemblage, the greatest variety of which, in one collection, may per- 

 haps be seen in the Museum of the late Mr. Cracherode, now united to that most invaluable 

 repository, the British Museum. 



