ANIMALS INHABITING UNIVALVES. 17 



Liruiasus ; they protrude neither tube nor foot beyond tlie shell ; 

 the pallium is divided ; they have only one large muscle, which 

 in many species leaves a conspicuous mark on the interior sur- 

 face of tlie shell, as in the common Oyster, Odrea edulis of 

 Linnaeus ; l)ut in many others the mark is not discernible, as 

 in most of the Scallops. This family includes the genus Ostrea, 

 with the Scallops or Pectines, tlie Sponcbjlus, a few Chamce, and 

 some of the Anomice. 



The next natural division (\he Mollusca with Heads of 

 Lamarck) includes the animals inhabiting the Argonauta and 

 the Nautilus, which are very little kno^^ n, and appear to beloiig 

 or are nearly allied to the Sepia or Cuttle-fish. It comprehends 

 also the animals of the rest of the Univalves, including the 

 Chiton, if we except Dentalium, Teredo, ajid Serpula. This 

 division consists of two families ; one having a windpipe or 

 breathing tube projecting more or less beyond the edge of the 

 shell nearly on the back of the animal, through a hollow 

 groove or cavity, which may be seen at the end of the shell 

 dirthest from the spire Q)l. 5. /. 59. a) ; and the other without 

 any such tube, and consequently without any hollow or notch 

 at the edge of the shell (/)/. 9. /. 118 and 1 1 9. a). The animals 

 of this division are furnished with a head, and horns or feelers, 

 generally two eyes, and with teeth which are very numerous 

 in some species ; they are all called Litnax by Linnaeus. 



The genera Conns, Cyprcea, Buccinum, Strombus, Murex, 

 vaih part of the Bidl^, and most of the Volutce, constitute the 

 family oi Limaces with a breathing tube. These, with scarcely 



D 



