GENEEAL CLASSIFICATION. 
Moll, 37 
J. D. Macdonald discusses the value of some characters employed in 
the classification of the Mollusca, pointing out the existence of several 
analogous genera, and analogous subdivisions of the Heteropoda and Pul- 
monata, and proposes the following system for the Gastropods : — 
Division I.— MONCECIA. 
Subdivision i. — Lingual dentition typically pavimental. 
Order 1. — Pneumonophora. 
Suborder 1. — Pulmonata. (a) Terrestrial, (b) Aquatic, 
(c) Estuary or marine. 
Order 2. — Apneumonopiiora. 
Suborder 1. — Nudihranchiaia. (a) Crijptohranchiata^ Phyl- 
liroe, Elysia, Limapontia, &c. (b) Phanero- 
hrancMata : Eolis, Doris, Tritonia, Phyllidia, 
&c. 
Suborder 2. — TectihrancMata : Pleurobranchus, Aplysia, 
Bulla, Tornatella, &c. 
Subdivision il. — Lingual membrane strap- or ribbon-like, rhachisand 
pleura distinctly differentiated, dental processes re- 
curved (Anaclodonta). 
Order 1. — Heteroglossa (Gray). 
Suborder 1. — Polyplacophora : Chiton, Chitonellus. 
„ 2. — Cyclohranchiai Patella, Patina. 
„ 3. — Cervicobranchia : Tectura, Gadinia, Lepeta. 
„ 4. — Cirrobranchia X Dentalium. 
Order 2. — Ehaciiidoglossa (Gray). 
Suborder b.—Dicranobranchia (Gray). Gills two, sym- 
metrical on the back of the neck: Dorido- 
branchus, Scutus, Emarginula, Puncturella, 
Fissurella. 
„ 6. — Schismatobranchia. Gills in two plumes on 
the left side of the gill cavity : Teinotis, 
Pudollus, Halictis, Scissurella. 
„ 7. — Scutihranchia. Gills in a spiral line on the 
left side : Stoniatella, Troclius, Turbo, Rotella, 
Nerita, Neritina, Navicella. 
„ 8. — Pseudobranchia. No distinct gills : Helicina, 
Proserpina, Ceres. 
Division II. — DICECIA. 
[The whole second subdivision of the author, the Scutibranchia and Cyclo- 
branchia of other authors, Rliipidoglossa and Docoglossa of Troschel, are 
not monoecious but dioecious, according to the observations of R. Wagner, 
Erdl. 1839, Milne-Edwards, 1840, Siebold, 1848, except Dentalium and 
its allies, which are also in other respects very far from the others. — 
Rec.] 
J. W. Spengel (Z. wiss. Zool. xxxv. p. 373) proposes the following 
classification of the Gastropods according to his researches into the 
formation of the nervous commissures (supra) ; — 
