578 



HISTORY OF SYSTEMS. 



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The divisions of the Phytophaga are — 1, the Heliciclae ; 

 2, the Trochidae ; 3, the Heliotidae ; 4, the Naticidae ; and 

 5, the Turbidae. Their analogies with the Zoophaga are 

 thus illustrated: — 



Families of the 

 Phytophaga. 



Helicid^s. 



Trochid.k. 



Haliotid^e. 



Families of the 

 Zoophaga. 



MuRIClD-E. 

 TuRBINELLIDjE. 



Naticid;e. 



Analogical Characters. 



Typical. 



Sub-typical. 



Foot enormously large; tentacula' 



very short; spire of the shell Volutidje. 

 very small. 



Shell highly polished, partly or p 

 { entirely covered by the mantle. } 



TuRBIDJE. 



Animal carnivorous ; mouth pro-"| 



bosciform, with a respiratory IStrombidjE. 

 I. siphon. J 



The order Dithyra is thus subdivided : — 1, the Macro- 

 trachia, where there are either one or two siphons ; 2, the 

 Atrachia, having none ; 3, the Tubulibranchia, or tubular 

 shell-fish, having an indistinct head, and an operculum to 

 their shell ; 4, the Cheliosomid^e, with a cartilaginous 

 covering and two orifices ; and 5, the Brachiopoda, or 

 anomian bivalves. The whole of these have their prototypes 

 in the Gasteropoda, as is shown in this table : — 



Tribes of the. , , . 



Analogies. 



{Animal with the mantle formed into' 

 an elongated siphon, simple or 

 double. 

 Mantle free, and without a siphon, 

 r Reciprocally representing- the Cepha-, m 

 i lopoda. } Tectibranchia. 



, Body cheloniform, oval, covered with • 

 testaceous or coriaceous plates. 



Dithyra. 



Macrotrachia. 



Atrachia. 

 Brachiopoda. 



Cheliosomid^e. 



Tribes of the 

 Gasteropoda. 



.Zoophaga. 



Phytophaga. 



]■ Cyclobranchia. 



m r Animal of the gasteropod structure, , „ 



Tubulibranchia. { hm[shed with * an ^{^ head> } Scutibranchia. 



