138 EEPTILIA. 



cranium, which will not admit of being included under the general 

 description already given. Thus, in the Chameleon, long processes 

 invariably project backward from the temporal and parietal bones, 

 and unite to form an arch, thereby occasioning a most singular form 

 of skull. The serpent-like apodal Saurians, as Pseudopus, Anguis, 

 have the head constructed completely upon the Saurian type, pre- 

 senting as in them the same style-shaped bone or columella which 

 occupies the place of the large alae of the sphenoid. Still more 

 abnormal are the conditions of the cranium in the Saurian genera, 

 Amphisbcena and Trogonophis, in which, however, the halves of the 

 lower jaw are firmly consolidated ; and also in those genera of Ser- 

 pents, which depart most from the Ophidian type, as Rhinophis, Tor- 

 trix, and particularly Typhlops, where the maxillary and nasal bones 

 form in front a hollow bony bladder, the pterygoid bones are repre- 

 sented by long squamoid bones, and the lower jaw, which in the 

 Rattlesnakes consists of three pieces, appears to be formed of one 

 piece, and to be edentulous. 



The Vertebral Column exhibits remarkable diversities in the several 

 orders of Reptilia. 



The vertebrae of the Icthyic Reptiles (Proteus, Siren, &c.) have 

 their bodies conically excavated at either end, and the intervals 

 between them filled up by a gelatinous substance, as in Fishes. The 

 number of the vertebrae is remarkable in the elongated bodies of the 

 animals belonging to this order, for 60 are to be counted in the 

 Proteus, 80 in the Siren, and above 100 in the Araphiuma. The 

 vertebrae are divided into those of the trunk and tail ; the first of 

 these presenting distinct and often strongly developed transverse 

 processes, and for the most part spinous processes also, which 

 entirely disappear at the extremity of the caudal series. The 

 number of the vertebrae is also very great in the Tailed Batrachia, 

 as in the spotted Salamander and Tritons, where there are 15 16 

 in the trunk, 20 30 in the tail, the numbers varying somewhat in 

 different individuals. The bodies are concave anteriorly, and con- 

 vex posteriorly ; the reverse of this is, however, the case in the 

 Tailless Batrachia, as the Frogs. These, as well as the Tree-frogs, 

 have but very few vertebrae, there being from 89 ; in Pipa there 

 are only 7, with stout transverse processes, which are especially 

 long upon the second and third lumbar vertebrae, to which succeeds 

 the single though large sacral vertebra, the transverse processes 

 of which are particularly broad. A long style or sabre-shaped bone 



