THE REPTILE G4LLERY. 



GENERAL NOTES ON REPTILES. 



There is but a short step from the Class of Birds to that of 

 Reptiles. No doubt, as regards external appearance, the dissimi- 

 larity between the living animals of these two classes is sufficiently 

 great to allow of a sharp line of demarcation being drawn between 

 them : Birds being shortly characterized as warm-blooded vertebrate 

 animals clothed with feathers, Reptiles as cold-blooded, and covered 

 with horny or bony shields, tubercles, or "scales." But there 

 are numerous and important agreements between these two classes, 

 especially in the structure of their skeleton, in their internal 

 organs, and their mode of propagation ; and their close relation- 

 ship becomes still more apparent when fossil forms, such as 

 Arch<sopteryx , are examined. 



Reptiles are termed " cold-blooded " because the temperature of 

 their blood is raised but a few degrees above, and varies with, that 

 of the outer atmosphere, owing to the imperfect separation of the 

 divisions of their heart, which allows more or less of a mixture of 

 '-the arterial and venous currents of the blood. Reptiles are ovi- 

 parous or ovoviviparous ; no important change takes place after 

 exclusion from the egg; they breathe by lungs throughout life. 

 Their skull articulates with the vertebral column by a single occi- 

 pital condyle (see fig. 1), and their lower jaw with the skull by a 

 separate bone (quadrate) (see figs. 1, 13, and 14). 



The remains of the oldest known Reptiles, those found in the 

 Permo-Carboniferous formations, belong to the Rhynchocephalian 

 type, of which onlyone representative is still living (in New Zealand). 

 Reptiles flourished and attained their greatest development in the 

 Secondary period — Pterosaurians (large flying Lizards, see Guide 



