CLASSIFICATION. 13 
the Gastrochenide, though, by the teeth, it is allied to the 
Veneres, but we consider the character of the teeth of very 
inferior value to the closed mantle, which points out its natural 
position. Teredo terminates the Acephala and passes them to 
the Dentaliade, our primary family of the Gasteropoda, agree- 
ably to the indices that are pointed out in the last page of the 
anatomy of Teredo. 
Third Division. 
LATERIBRANCHIATA. 
GASTEROPODA CYCLOBRANCHIATA. 
CERVICOBRANCHIATA. 
The animals of this division are strict hermaphrodites with- 
out congression. The Dentaliade are the Lateribranchiata of 
the synopsis, of which family I have already given in the 
‘Annals of Natural History’ a detailed anatomy; they have 
claims which appear not to be ill-founded, to stand as the first 
family of the Gasteropoda, from the connection between them, 
by the position of the branchiz, with Teredo, the last family of 
the Acephala. The Chitons are the Cyclobranchiata. The 
Patelle, Acmea, Pileopsis, and Calyptrea are the Cervico- 
branchiate patelloid forms with a single non-symmetrical 
branchial plume ; and Fissurella, Emarginula, Puncturella, and 
Haliotis are mm the same Cervicobranchiate category, but 
differ from the first patelloid group in having two symmetrical 
branchial leaves. 
Fourth Division. 
CRYPTIBRANCHIATA. 
PLEUROBRANCHIATA. 
PULMONIFERA. 
PARS-PECTINIBRANCHIATA. 
GASTEROPODA 
In this division there is an important advance im sexual 
arrangement ; pure hermaphroditism iseabandoned, and that of 
mutual congression has succeeded. The families are the Plew- 
robranchide, Aplysiade, Bullide, Pulmonifera, Pteropodide, 
