514 



MOLLUSC A. 



This is ;i small family, tin- typical 



THE POLISHED NBRITA. 



THE NKRITID.E. 



species of which, Ncrites ustulata, are called Sea-Snails : 

 they have a thick and rather globose shell, and are mostly 

 marine ; those of tlic genus Neritina, however, inliabit fresh 

 water. The Polished Nerita, Nerita j^olita, is distrib- 

 uted through nearly all tropical seas. 



THE PALUDINID^. 

 This family includes several genera, having somewliat glo- 

 bular shells, with a thick olive-green epidermis. The River- 

 Snail, Paludina Listeria has a turbinated shell, with round 

 whorls. Found in the Caspian and Black Seas. The Ap- 

 ple-Snail or Idol-Shell, Ampullaria globosa, has a globular shell and a large ventricose body- 

 whorl ; found in the West Indies, South 

 America, &c. The A. dubia is found in the 

 Nile. Several species of this genus, brought 

 from Egypt to Paris packed in bran, were 

 found living, though they had been four 

 months in making the passage. 



THE NATICIDJi:. 



In these the shell, which is globular, com- 

 posed of live whorls, and has an entire aper- 

 ture, is partially inclosed in the mantle. The 

 Natica canrena, found in various seas, is 

 blind ; it frequents sandy and gravelly bot- 

 toms, ranging from low water to a depth 

 of ninety fathoms. 



THE IANTHINID.E. 

 These are carnivorous and oceanic, and 

 possess shells almost exactly resembling 

 those of the land-snail; they are without 

 eyes, and secrete a sort of operculum, which 

 operates as a float, bearing them about upon 

 the water. They occur in vast numbers in 

 the Atlantic, and are sometimes driven by 

 storms upon the coasts of Great Britain ; 

 the same happens on our shores. In 1839, 

 great numbers of them were washed upon 

 , the beaches of Nantucket. 



THE CALYPTR^ID^. 

 These, called Bonnet Lim2)ets, have a lim- 

 pet-like shell, which is usually somewhat 

 spiral at the apex ; they appear to pass a 

 sedentary life, attached to stones and rocks. 

 Of the widely distributed genus Cali/])ira!a, 

 of which the Cup-and-Saucer Limpet, C. 

 eguestris, is the type, fifty species are known. 



THE AMPULLARIA DUBIA. 





THE EAR-SHELL. 



THE HALIOTID^. 

 In these, which are called Ear- Shells, the 

 animal has a short muzzle and two branchial plumes ; the shell has a spiral conformation, and the 

 perforations for the anal siphon are arranged in a row along the back of the shell. The Tuber- 



