18 ANIMALS INHABITING UNIVALVES. 



any exception, inhabit water, and liave only two horns ; tlie 

 eyes are placed at the root of the horns, or at some part of 

 their side, but never quite at the end or tip Qpl. 5. /. 59) ; 

 several of these animals are furnished with a cylindrical trunk 

 or proboscis, at the end of whicli is the mouth fornished with 

 small teeth of a hook-like form, with which the animal pierces 

 other shells, and then sucks the flesh of the inhabitants for its 

 food (p/. 10. /. 1). 



The family oi Limoces without a breathing' tube, of which 

 tlie Garden Snail is a familiar example, comprehends the re- 

 maining' species of the genus Bulla and Voluta, and all those 

 ofTrochus, Turbo, Helix, Nerita, Haliotis, Patella, and Cldton. 

 The water species have generally two horns, except the Chiton 

 and some Bulla. The eyes in some are placed on the head or at 

 the side of the horns ; but many of the animals have, besides 

 the horns, a short kind of column or pillar at the outside of 

 each horn (;)/. 9. /. 119. a), with the eyes placed at the tip of 

 them, as in most of the Neritce. All the land species belong 

 to this family ; these have four horns, with the eyes at the tips 

 of the longest ; but none have the trunk or proboscis noticed 

 in the other family. 



OF THE SHELLS. 



Of the shells we may observe that the two valves or pieces 

 of which the Bivalves are composed are in general more or less 

 convex ; in a great number both valves are equally so ; in 

 many, one is more convex than the other ; but in some few 



