195 



CHAP. VII. 



THE PHYTOPHAGOUS GASTROPODS CONTINUED. THE TUREID-«, 



OR MARINE SNAILS. 



(180.) The family of Turbid^ succeeds the last, 

 and, like them, is composed of spiral shells, destitute 

 of any pearly lustre, with the aperture closed by an 

 operculum * : the differences, however, are so slight, 

 that the two families can scarcely be distinguished by 

 their shells alone. The animals of the Turbidce, hov/- 

 ever, are remarkably dissimilar from those of the 

 Helicidcp : they breathe by gills, like all the zoopha- 

 gous families ; and, like them, the mouth of the major 

 part is furnished with a respiratory siphon, and even 

 a probosciform mouth : the tentacula are only two ; 

 and the eyes are either basal, or on the sides of the 

 tentacula. The animals, in short, often exhibit the 

 carnivorous structure of the Zoophaga, while their shells 

 are completely those of the phytophagous tribe : it is 

 thus that the two groups are connected. The whole of 

 this assemblage are comprised in the following sub-fami- 

 lies : — The first is uncertain. 2. The AmpullarincB, or 

 apple-snails. 3. The Melaniance, or black snails. 4. The 

 Turhince, or winkles. 5. The lantltincE, or Oceanic 

 snails. A general analysis of these will now be given ; 

 this investigation we were, in a manner, forced into, 

 from the impossibility of discovering any bond of union 

 or of affinity between the heterogeneous genera of the 

 Turbidce, as they now stand in our conchological 

 systems. 



(181.) The first primary division by which this 

 family may be united to the fluviatile Limnacince, is 



* Except in Melampus, and probably lanthina, 



o 2 



