378 



GASTEROPODA. 



are hermaphrodite with reciprocal impregnation, 



and marine. 



1st Sub-order, Pliyllidiadtr, Cuv. 



1st Fam. Phi/lfiJia, fig. 17.5. 

 2d Sub-order, Semi-phyludicube, Lam. 



2d Fain. Gattropuu, Blainville. 



3d Fam. Pleurobranc/nis, Cuv. 



Fig. 175. 



Order III. TECTIBRANCHIATA* 



(Cuv.) 



Syn. Chismobranches, Blainville; Gast. 

 Adtiobranches,-^ Dumeril; Gait. Phyllidiens 

 and Laplysient, Lamarck. 



In this order the branchiae are placed upon 

 the dorsal aspect of the body, but are pro- 

 tected by a fold of the mantle which almost 

 always contains a shell presenting a rudimen- 

 tary spire. They are all hermaphrodite like 

 the preceding, and marine. 



1st I'am. Dikera. 



2d Fam. Akera. 



Order IV. PULMONALIA INOPER- 

 CULATA, (Ferussac) 



Syn. Piilmones, Cuv.;J Pulmobranchcs, 

 Blainville; Gust. TracJielipodetf) Lamarck. 



The respiratory apparatus is here adapted to 

 the respiration of atmospheric air, and instead 

 of being composed of branchial tufts or la- 

 minae, consists of a cavity lined by the rami- 

 fications of the pulmonary vessels, the entrance 

 to which can be opened or closed at the plea- 

 sure of the animal. Almost all the species 

 are provided with a shell either turbinated or 

 concealed within the mantle, but are never 

 furnished with a calcareous operculum. Every 



Tectas, covered. 



t AJtXoj, concealed. 



J Pulmo, lunqs. 



$ Tpajc" x '> l/f neck ; nan, foot. 



individual is hermaphrodite, but mutual copu- 

 lation is essential to fertility. Some are terres- 

 trial, others inhabit fresh water, and some are 

 marine. 

 1st Sub-order, Gcophilidte,* Ferussac. 



1st Fam. Limax. 



2d Fam. llcli.r. 

 2d Sub-order, Gchydrophilidtr,) Ferussac. 



3d Fam. Auricula. 

 3d Sub-order, Hygrophilid<t,l Ferussac. 



4th Fam. Limnaus. 



Order V. PULMONALIA OPERCU- 

 LATA, (Ferussac.) 



Syn. Pectinibrancltiataf) Cuv. ; Siplwni- 

 liranc/iiuta,\\ Blain. 



The respiratory organs of the animals form- 

 ing this order are similar in structure to those 

 found in the last, but they differ materially in 

 other points. In all the operculated division 

 the shell is closed by a calcareous operculum 

 not found in the last, and instead of that 

 hermaphrodite condition of the sexual organs 

 common to the inoperculated order, the sexes 

 are distinct, the male and female parts existing 

 in different individuals. They are all terres- 

 trial. 



1st Fam. Helicina. 



2d Fam. Turbiclna. 



Order VI. PECTINIBRANCHIATA, 

 (Cuv.) 



Syn. Trachelipodes, I-amarck ; Monopleuri- 

 branches, Blain. ; Gast. Adelobranchet and 

 Siphonlbrmifhes, Dumeril. 



This extensive order, which comprises most 

 of the univalve mollusks whose shells enrich 

 our cabinets, is characterized by a respira- 

 tory apparatus adapted to an aquatic medium. 

 The branchiae are pectinated, consisting of 

 ranges of fringes disposed like the teeth of a 

 comb, and generally enclosed in a dorsal cavity 

 which opens externally at the side of the body 

 or above the head. The shell is always turbi- 

 nated, and sometimes provided with an oper- 

 culum. The sexes are separate, and the ani- 

 mals fluviatile or marine. 

 1st Sub-order, Pomeatomidte, 1 ^ Ferussac; Chis- 

 mobranches, Blainville. 



1st Fam. Turbo, Lin. 



2d Fam. Trochus, Lin. 

 2d Sub-order, Hemipomattomidt, Ferussac. 



3d Fam. Cerithium, Adanson. 



4th Fam. Kuccinum, Lin. 



5th Fam. Murci, Lin. 



6th Fam. Stromlius, Lin. 



7th Fam. Conns, Lin. 

 3d Sub-order, Apmnastomid<c, Ferussac. 



8th Fam. 



9th Fam. Valuta, Lin. 



10th Fam. 

 4th Sub-order, Adelodermidt, Ferussac. 



llth Fam. Sigairliix, Adanson. 



* rn, the earth ; <f>iXE, to lore. 



t Pu, the earth ; ubvp t the water ; <fnXi. 



t T >7C, moist; <t>lXE. 



Pecten, -inis, a cwnb. 



|| Si<pv, a canal. 



^f uifj.a., ojierculum ; CTT/X, mouth. 



