REPORT ON ZOOLOGY. 177 



detail, and given minute descriptions of the teeth as they occur 

 in all the different genera in the above two orders. 



Among the Ophidia more perhaps remains to be done than 

 in any other order of Reptiles. Many new genera and species 

 have been discovered of late years, and described by different 

 authors ; but of several the characters and synonyms are ill 

 determined, and their affinities still more so. Mayer has pro- 

 posed a new arrangement of this group*, fomided on the pre- 

 sence or absence of rudimentary posterior extremities, which he 

 has succeeded in detecting in many genera in which they were 

 not before known to exist. He would adopt as three subordi- 

 nate divisions : 1. Phcenopoda, \n which these, extremities are 

 externally visible ; 2. Cryjitopoda, in which they are entirely 

 concealed beneath the skin ; 3. Chondropoda, in which the ru- 

 dimental feet are reduced to mere cartilaginous slips, and Apoda, 

 in which they are entirely wanting. M. Duvernoy, in the Ann. 

 des Scien. for 1832t, has entered upon the consideration of the 

 anatomical characters which serve to distinguish the venomous 

 from the innocuous serpents. As these groups are kept distinct 

 by Cuvier, as well as by some others, in their systematic ar- 

 rangement of the Ophidia, such researches may prove service- 

 able to the zoologist in helping him to the true situation of some 

 genera. In a later volume of the same work+, M. Duvernoy 

 has followed up this inquiry, as well as treated of some other 

 parts of the internal organization of serpents in general. On 

 the subject of the alimentary canal, he particularly observes that 

 it offers sensible differences in different genera, and such as may 

 serve to confirm or lessen the propriety of adopting some of those 

 which have been established by naturalists. In this last com- 

 munication, he has also made some remarks § on the forms and 

 arrangement of the scales on the head and body considered as 

 zoological characters. He thinks that such characters require 

 to be compared afresh with those derived from the internal 

 structure, in order that their true value may be more correctly 

 ascertained. The genus Ccocilia, which by some has been asso- 

 ciated with the true Reptiles, by others with the Amphibia, has 

 been recently discovered by M.Miiller|| to possess gills in the 

 very young state, which fact seems to corroborate its claims to 

 a place in the class last mentioned. 



The structure of the Amphibia has been much studied of late 

 years, and has given rise to many excellent memoirs on the part 

 of different observers. As these, however, are for the most part 



* Nom Acta Acad. Nat. Cur., torn. xii. p. 819. f torn. xxvi. p. 113. 



X toni. XXX. pp. 5 and 113. § p. 25. 



Il Ann. des Scien. 1832, torn, xxv. p. 89. 

 1834. N 



