86 AMERICAN JOURNAL 



II. Heteroglossata. — Dentition more distinct by the failure of 

 the subulate marginal teeth. 



Cjclobranchia. Patella, Chiton. 

 Cirribranchia. Dentalium. 



Class IV.— ACEPHALA. 



Sexes separate (except with Ostrea and Pecten, which are 

 hermaphrodite.) Without copulation ; fecundation by the dis- 

 persion of semen. The larvae are provided with two wings, 

 ommatophorous, and tentaculated, as the Gasteropods. The 

 metamorphosis is, therefore, retrograde (Lovln) 



1. Dimyaria. 



2. Heteromyaria, {Mytilaceal) 



3. Monomyaria. 



The Cephalopods do not differ more from the Gasteropods, 

 than the gymnosomous Pteropods. Their long arms corre- 

 spond to the prehensile collar of the Pneumoderms ; their short 

 arms, furnished with cups, are likewise recognized in the 

 (jymnosoms. Their funnel corresponds with the foot of the 

 Gasteropods, but their heart and their copulative organ are 

 not sufficiently known to permit us definitely to indicate their 

 place. 



The thecosomous Pteropods (Ilyakea, etc.) differ from the 

 gymnosomous Pteropods by their teeth, which are disposed in 

 three rows, and by their fins, which correspond to the cephalic 

 velum of the Olives, and not with the epipodium of the 

 Gymnosoms. According to the anatomy given by Souleyet, 

 in the ''Voyage of the Bonite," these animals are undoubtedly 

 androgynous. I have, in the "Malakoz. Blatter," 1859, given 

 more extended notices of these subjects. The ancient groups 

 based on the form of the foot, correspond with those of Klein 

 for the Vertebrates: Apoda, Bipeda and Quadripeda (including 

 the Reptiles.)* 



* M. Crosse proposes, in a future No. of the " Journal de Conchylio- 

 logie," to attack the system of classification indicated above. We will fur- 

 nish our readers with a translation of this paper also, as soon as we receive 

 it. We have already stated our opinion, that the dentition is of much less 

 value in classification than is generally accorded to it. 



