chiton. 391 



CHITON, Linn/bus. 



Shell oblong, composed of eight transverse plates, imbri- 

 cating, variously ornamented on their surfaces ; all lodged 

 in a coriaceous mantle which forms an expanded, smooth, 

 shagreened, wrinkled, granulated or spiny margin all 

 round the body. 



Head of the animal obscurely defined, formed of a pro- 

 boscis covered by a fleshy semicircular hood, no tentacles 

 nor eyes; buccal mass with cartilaginous jaws, lingual rib- 

 band long and linear, furnished with numerous transverse 

 series of teeth, of which three in each series belong to the 

 rachis, flanked on each side by a single large uncinated 

 lateral tooth and a supplementary lateral, the last arising 

 from among five polygonal flanking plates. Branchice 

 forming a series of lamellae between the mantle and foot 

 on each side ; foot an oblong disk, rounded at each 

 extremity. 



These curious mollusks constituted part of the " multi- 

 valves "of old conchologists, and cannot be mistaken for 

 members of any other genus or tribe. They are distri- 

 buted all round the world, and the species are very 

 numerous ; often very curious and even beautiful. They 

 live attached to rocks, stones, and shells ; more rarely 

 are they found creeping on sand. They inhabit various 

 depths of water ; the majority of species are littoral or 

 sublittoral, but a few range to great depths. From their 

 fragility few traces of fossil species might be expected to 

 be found ; nevertheless, even as far back as the palaeozoic 

 epoch it would appear that Chitons were in being. 



We retain the genus Chiton in its original signification, 

 deeming that, in the present imperfect state of our know- 



