GUPPy : MOLLUSCA OF TRINIDAD, 225 



D'Orbigny's Paludina pisciitm, parchappii, and perhaps 

 also austialis (Amer. Merid.) and Paludestrina affinis (Moll, de 

 Cuba) are very probably forms of this species. Pahidestrina 

 candeana and auberiana are quoted from Guadelupe by Maze 

 in 'Journ. Conch.,' 1883 (p, 32). The distribution of the 

 species is probably very wide, and includes the West Indies and 

 tropical South America, and, perhaps, also, Central America, 

 In my above-quoted account in the ' Annals and Magazine of 

 Natural History' the word 'moniliform' was not, perhaps, 

 judiciously used ; it was merely intended to denote an incircling 

 row of spines or small tubercles, 



41. Ampullaria cornu-arietis L, 



D'Orbigny, Voy. Amer. Merid. pi, xlviii., f. 7 — 9. 



Woodward, Man, Moll., pi. ix., f 31, 



Crosse, 'Journ. de Conch.,' 1890, p. 53, No. 46. 



The noticeable differences between the typical (globular) 

 AmpullaricE, and those of the section bearing Gray's name 

 Marisa (or Guilding's Ceratodes). of w^hich the present is the 

 typical species, are that the shell is planorbiform, and nearly 

 but not quite symmetrical, the animal without a long siphon 

 and the operculum thinner. The form of the shell and the 

 organization of the animal adapt it for life in ponds, bayous 

 and backwaters, where its favourite aliment is the water-lily and 

 other aquatic plants, 



42. Ampullaria urceus Miill, 

 Wood, Ind. Test, Helix, 72. 

 Crosse, 'Journ. de Conch.,' 1890, p. 53, No. 47, 



A giant among freshwater shells, as Bnliimis oblongus is 

 among land shells. It has much the same geographical distri- 

 bution as that mollusc. It frequents the larger streams in great 

 numbers, and buries itself in their beds or banks in seasons of 

 drought. 



