MOLLUSCA OR UNIVALVES. 143 



tough ligament. Animal, head not very dis- 

 tinct; no tentacula nor eyes, but having a long 

 tongue rolled spirally, and armed with horny 

 teeth; foot long. — 70 species recent, 1 fossil. 



The ligament of this shell is sometimes 

 fleshy, smooth, or wrinkled, covered with scales 

 or tufts of hair ; and in one species, the Chi- 

 ton spinosus, it is armed with numerous thin 

 long black spines. The interior of the shell is 

 generally white ; but some are green, and one 

 species is of a beautiful rose colour. They 

 often attain a large size, measuring several 

 inches in length; but do not usually exceed 

 two inches. They are found in most seas, 

 the larger species coming from warm lati- 

 tudes. Several, of a small size, are found on 

 the British coast. They have the power of 

 rolling themselves up into a ball, like the 

 woodlouse or the hedgehog. 



17. Patella. — Shell simply conical, with- 

 out any perforation or internal appendage, and 

 with the margin undivided ; apex inclined to- 

 wards the front part of the shell, where the 

 head of the animal is situated, the mark of which 

 can generally be traced in the interior by its 



