APPENDIX. 345 



Suborder 2. Tectibranchiata (Pleurobranchus, Aplysia, 

 Bulla, Tornatella, etc.). 

 Subdivision II. Lingual membrane strap- or ribbon-like, rhachis 

 and pleura distinctly differentiated, dental processes re- 

 curved (Anclodonta). 

 Order 1. Heteroglossa (Gray). 

 Suborder 1. Polyplacophora (Chiton, Chitonellus). 

 Suborder 2. Cyclobranchia (Patella, Patina). 

 Suborder 3. Cervicobranchia (Tectura, Gadinia, Lepeta). 

 Suborder 4. Cirrobranchia (Dentalium). 

 Order 2. Rhachidogiossa (Gray). 

 Suborder 5. Dicranobranchia. Gills two, symmetrical on 

 the back of the neck (Scutus, Doridobranchus, Emargi- 

 nula, Puncturella, Fissurella). 

 Suborder 6. Schismatobranchia. Gills in two plumes on the 

 left side of the gill cavity (Teinotis, Padollus, Haliotis, 

 Scissurella). 

 Suborder 1. Scutibranchia. Gills in a spiral line on the left 

 side (Stomatella, Trochus, Turbo, Rotella, Nerita, Neri- 

 tina, Navicella). 

 Suborder 8. Pseudobranchia. No distinct gills (Helicina, 

 Proserpina, Ceres). [Nearly all of the groups of subdi- 

 vision II of " Monoecia," are known to be dioecious. — G. 

 W. T., Jr.] 

 Division II. Dioecia. 

 Subdivision I. Lingual membrane unarmed, or with pleural 

 teeth only. 

 Order 1 (without name). 



A. Rhachis and pleurae unarmed (Pyramidellidte, Cancel- 



lariidse). [Cancellaria has an armed radula.] 



B. Pleural teeth simple [Toxoglossa, Troschel] (Pleuro- 



tomidffi, Acusidse, Conidse). 



C. Dentition, Pavimental [Ptenogiossa, Troschel] (Sola- 



riidae, Scalariidse, lauthinidse). 

 Subdivision II. Lingual membrane strap- or ribbon-like. 

 Order 1. Proboscidifera. 

 Suborder 1. Orthodonta. Dental processes pointing directly 

 backwards [Rhachiglossa, Troschel]. 



A. Lingual dentition uniserial (Yolutidae [See suborder 



II]). 



B. Lingual dentition triserial. 



a. Rhachis and pleurae comb-like. 

 ■ Dental processes numerous, small. 



Strap short (Mitridse). Strap long. Teeth short 

 (Fasciolariidse). Teeth long (Fusidse). 

 Dental processes few and large (Turbinellidai). 



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