THE REPTILE GMLERY. 



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(Bopteryx, 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 ii^^ ; they breathe by lungs throughout life. 

 Their skull articilates v/ith 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 

 Pernio-Carboniferous formations, belong to the Rhynchocephalian 

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

 Reptiles flourished and attained their greatest development in the 

 Secondary period — Pterosaurians (large flying Lizards, see Guide 



