Nora Ada Acad. Ca'.snr. Xaiura; Citnosor?nn. 253 



being tliick and conical in the 0. riifiis, and slender in the O. 

 Jmscus. 



In the Memoir which we have now to notice, '' Uber (^ie 

 hintere extremitiit der Ophidien," a most important fact, and 

 highly illustrative of the manner in which all Vertebratcd Animals 

 resolve themselves into one common type, is placed in the clearest 

 light by the investigations of Professor Mayer. It is known that 

 many of the Cartilaginous Fishes possess a kind of posterior limb, 

 and it was natural to suppose that animals of a higher class, such 

 as Serpents, would not be found wholly destitute of a similar 

 organ. That a rudiment of this organ actually existed in the 

 claws or spurs, as they have been termed, of the Bocc^ has been 

 suspected by several distinguished Naturalists ; but it was re- 

 served for the authour of the present Paper to investigate the sub- 

 ject thoroughly, and to prove by the anatomical examination of a 

 great number of Snakes of different genera, the complete analogy 

 which exists between the imperfect structure found in the latter, 

 and the posterior members of other Reptiles. The results of his 

 labours, as far as they have been hitherto carried, have induced 

 him to propose a new division of the Order into PiiiENOPonA, 

 consisting of those Snakes whose rudimental feet are externally 

 visible, and comprising Bor/, Python^ Eri/x, Clothonia^ and 

 Tortrix ; Crypto poda, in which the bony rudiments are entirely 

 concealed beneath the skin, containing yl/ign/s^ Ti/pJilopx, and 

 Amphisbcena ; and a third family, in which the rudimental feet 

 consist merely of cartilaginous slips (Ciiondropoda), or are en- 

 tirely wanting (Apoda). To the latter family belong Coluber^ 

 (in one species only of which, the C pullatus, Dr, Mayer dis- 

 covered, in the same situation with the foot-rudiment in the pre- 

 ceding Snakes, a tolerably strong curved cartilage,) Crotalus and 

 Trigonocephcdiis (in which no traces of this organ could be dis- 

 covered), and lastly the enigmatical genus Ca'ciliUy which is equal- 

 ly destitute of tail and of foot rudiments. 



The description of these rudimental appendages is given at con- 

 siderable length, especially in the genus Boa, in which the claws 

 are more promineiit externally, and the internal parts of the organ 

 more fully developed, than in any other Snakes. The bony 



