OP CONCHOLOQY. So 



Metamorphosis out of the egg (larva swimming.) 



c. Marina. Ceritliium, Tnrritella. 



Metamorphosis within a sac. 



d. Parasitica. Vermetus, Calyptrsea, Hipponyx. 



e. Pelagica. Htteropodi. 



B. Proboscidi/era. — -Mouth at the extremity of a retractile 

 proboscis. Larva swimming. Natica, Cassis, Dolium, 

 Triton, Ranelli. — Proboscis not retractile, Cyprsea, 

 Strombus. 



II. Rachi gloss ata. — Lingual teeth disposed in three longitu- 



dinal rows, simply sharp, not curved, (except Voluta, 

 which has but one row.) Mouth at the extremity of a 

 retractile proboscis. Eggs enclosed in corneous cap- 

 sules. (Melicertigenes.) — Marginella, Voluta, Harpa, 

 Oliva, Nassa, Buccinum, Fasciolaria, Fusus, Murex, 

 Twbinella, Purpura, Columbella, Mitra. 



III. Toxoglossata. — Lingual teeth subulate, with an external 



or internal veneniferous canal. Gancellaria, Terebra, 

 Clionella, Pleuro/oma, Conns. 



Series II.— DIOCORDIA. 

 Heart trilocular, with two auricles surrounding the rectum. 



Class III. — PSEUDOPHALLIA (AsPIDOBRANCHIA, Ol'im.) 



Sexes separate, but without external male organ. The 

 question of copulation in this class, or the mere di.-persion of 

 semen, as with the Acephala, is undetermined. The heart is 

 provided with two auricles, even with the genera which have 

 not more than a single branchia. (See "Voyage of the Astro- 

 labe, 11 Anatomy of Turbo marmoratus.) Development known 

 only in Chiton and Dentalium. 



I. Rhipidoglossata. — Lingual teeth numerous, disposed in two 

 orders, the marginal ones aciculatc and turned into 

 hooks. 



a. Terrestria. Helicina. 



b. Fluviatilia. Neriti.na. 



c. Marina. Nerita. 

 Trochoidea, [Ha liotis.) 

 Fissurellidea. 



