183 
MISCELLANEOUS. 
On the Classification of the Gasteropodous Mollusca. 
By M. Gourter. 
A piviston of the Gasteropoda founded on the generative organs 
presents this radical defect, that many species reputed to be herma- 
phrodite are constantly being found to be unisexual, and further that 
Mollusca evidently nearly allied, such as the Helices and Cyclo- 
stomata, are necessarily separated on the consideration of their sexual 
organs. 
Therefore most authors have justly selected the respiratory ap- 
paratus as the basis of classification, since the position of this 
organ determines the position of the heart and generally that 
of the anus. In the classifications generally followed, such as 
that of Cuvier, however, orders are found to be established upon 
various characters of unequal importance although generally derived 
from the respiratory apparatus. Thus the Nudibranchs are gene- 
rally characterized by their uncovered branchie, although with a 
restriction for the separation of the Inferobranchs, which are really 
also Nudibranchs. Elsewhere only the pectinated form of the organs is 
considered, as in the Pectinibranchs, although in other divisions, such 
as the Tectibranchs, this form of the branchiz sometimes occurs. 
The term Tectibranch also conveys to the mind the same sense as 
Scutibranch. The expression Tubulibranch would seem to indicate 
a tubular form of the branchiew, when it only refers to the tubular 
form of the animal. In the case of the Heteropoda the branchize 
are set aside, and a character of subordinate value, the form of the 
foot, is set on the same level as those of the preceding divisions. 
The word Cyclobranch would perhaps be the most suitable, but for 
the confusion between them and the Inferobranchs, if taken literally. 
In fact, in the establishment of orders, the position and form of 
the branchiz, the form of the foot, and the general form of the 
animal have all been placed in the same rank, without assigning to 
any one of them a marked preeminence over the others. To remedy 
this defect the author proposes, taking the respiratory apparatus as 
his basis, to select the most important of its characters, and to esta- 
blish the primary divisions upon this. He considers the position of 
the branchie to furnish the most important character. The bran- 
- chize can only occupy three positions: they are either 
Completely external ; 
Or completely internal, and then concealed in a cavity which is 
itself covered by a shell which usually envelopes the animal ; 
Or simply protected by an impertect test, a condition intermediate 
between the two preceding. 
Hence, after the separation of the Pulmonata as a distinct sub- 
class, we get three great divisions,—the Exobranchs, the Stegi- 
branchs, and the Endobranchs. 
I. The order of Exoprancns may be subdivided, according to 
the point of the surface upon which the branchiz are inserted, into— 
