424 Anuli/lical Notices of Books. 



insufficient to constitute a generic distinction. It is however 

 divisible into two genera, corresponding with the two systems of 

 dentition which it presents, and which agree with the two different 

 structures of their crania. In each of these genera there are 

 flying, and not flying, species. To the Phalangers with com- 

 pound teeth he gives the generic name of Petaurus^ reserving that 

 of Phalangista for those the teeth of which are simple ; but as he 

 proposes at a future period to enter into more detail on the sub~ 

 ject, we shall defer our furthernotice, merely remarking that the 

 P. Cookii, in the description of which these observations occur, 

 is a Petaurus of M. F. Cuvier. 



Memoir es du Museum d^Histoire Naturelle. — Sixieme Annee, 

 Cahiers. vi. — x. 



Of the zoological contents of the present portions of the 

 Memoirs of the Museum of Natural History, which consist of 

 papers from the pens of MM. GeofFroy Saint-Hilaire, Isidore 

 Geoffroy Saint-Hilaire, and Duponchel, there is much which is 

 incapable of analysis. Of this description is the exposition by the 

 former of these Zoologists of his theory with respect to the oper- 

 cular or auricular fin of fishes ; a theory which in a subsequent 

 number he is under the necessity of defending from the attack on 

 it by M. Cuvier in the Ossemens Fossiles. Connected as it is 

 with his peculiar views of the structure and composition of the 

 Cranium, it is impossible to convey a correct idea of it without 

 entering into much greater detail than our space will permit. 

 For the same reason we must also pass by the researches of this 

 philosophic Natunilist <•' on the organization of the Gavials," 

 (the Crocodili longirostres of the Ossemens Fossiles,) " on their 

 natural affinities, from which results the necessity of anew generic 

 distribution, Gavialis, Teleosaurus, and Steneosaurus ; and on 

 the question, whether the Gavials now found in the eastern parts 

 of Asia descend by a series of uninterrupted generations from the 

 antediluvian Gavials, either from the fossile Gavials termed Cro- 

 codiles of Caen (Teleosaurus,) or from the fossile Gavials of 



