CLASSIFICATION. 65 



Sect. 1. Marginella, Yolnta, Volutilithes, connecting with 

 Cryptochorda and Harpa ; Oliva, Ancillaria, Bullia, Nassa, 

 Mitra, Columbella. 



Sect. 2. Buccinum, Fasus. Fasciolaria, Turbinella, Purpura, 

 Mnrex, Magilus. 



Order 3. Toxoglossata. Two rows of teeth. Stimpson 

 has recently discovered a median tooth in ClioneDa sinuata, 

 Born. Conns, (Borsonia?), Plenrotoma, Clionella, Terebra, Can- 

 cellaria, Halia, Lachesis ? 



Supra Class II. Agama, Latr. (Diotocardia, Morch). 



Mollusks without copulative organ. Heart with two auricles, 

 placed nearly always around the intestine. 



Class 1. EXOCEPHALA, Latr. (Pseudophallia, Morch). 

 Order 1. Ehtpidoglossa, Troschel. Proserpina, Helicina, 

 Hydrocena, with sessile eyes. 



Gray, in figuring the teeth of Proserpina (Ceres), formed for 

 this mollusk a distinct suborder, alongside of the Neritinte, which 

 he called Pseudobranchia. In the same year (1857) Morch 

 placed Helicina? in the Rhipidoglossates, with Neritina, notwith- 

 standing the want of an operculum in Proserpina, an example 

 followed by Troschel with some hesitation. 



Eyes sessile. Shell not nacreous. Neritina, Nerita. 



Shell nacreous. Phasianella, Turbo, Trochus, Margarita, 

 Stomatia, Haliotis. 



Ej^es not petiolate. Shell not nacreous. ? Scissurella, Emar- 

 ginula, Pissurella, the affinity of which with Haliotis, is incon- 

 testable. 



Order 2. Heteroglossata, Gray. (Orthodonta, Morch, 

 Docoglossa, Troschel.) Patella, Tectura, Pilidium, etc., Chiton. 



Class 2. ACEPHALA, Cuvier. (Endocephala, Latreille ; 

 Dithyra, Anst.) 



Dimyaria (Plagymiona, Latr.). 



Heter amy aria (Mytilacea). 



Monomyaria (Mesomyona, Latr.). 



Notwithstanding that the systematic value given above to 

 these different groups varies from that of other authors, their 

 order of succession differs but little from Cuvier. The separa- 



