them together in one family (Sauropsida\ contrasted on the one 

 hand with Ichthyopsida (Amphibia and Fish), and on the other with 

 the Mammalia. Sauropsida have an epidermic exo-skeleton and a 

 single occipital-condyle. The lower-jaw is connected with the 

 skull by a quadrate-bone ; some of the blood-corpuscles are 

 nucleated. All are oviparous or ovoviviparous, with the exception 

 of the Chelonia. The shape of the body of a Reptile is very 

 variable, elongated, and usually provided with four limbs, some 

 have two only, and some are limbless and serpentine. The 

 vertebrae are more or less ossified. Chelonidce and some extinct 

 Reptiles are destitute of teeth. The heart consists of two separate 

 auricles (a right and a left), and an incompletely divided ventricle. 

 The arrangement to counteract this incomplete division, by which 

 the venous and arterial streams are kept separate more or less 

 and prevented from being completely mixed, deserves notice with 

 Crocodilia only. Of all Reptiles the partition between the right 

 and left halves of the ventricle is complete in the Crocodilia only, 

 so that the right-side deals wholly with venous blood and the left- 

 side with arterial^ All Reptiles respirate through lungs, the 

 skull is larger and the brain exhibits an advance on Fish and 

 Amphibians. With regard to their distribution in time, the 

 earliest Reptilian remains have been found towards the close of 

 the Palaeozoic Age in the Permian rocks, where we meet with 

 representatives of Lacertilia which do not seem to differ much 

 from Lizards which are now living. 



Chelonia is the first Order of Reptiles. It comprises Tortoises 

 and Turtles, distinguished by the following characters : They 

 have an endo-skeleton connected with an exo-skeleton (a bony 

 case in which the body is enclosed). This is covered by 

 horny-plates, and in some instances by a leathery-skin. 



The dorsal portion of the case has three series of plates, of 

 which five are median, and four on each side, their outer margins 

 guarded by twenty-four or twenty-five plates. Those connate 

 with the neural-spines, eight in number, are termed neural-plates. 

 The plastron or ventral shield, unlike the carapace, is 

 wholly exo-skeletal, as no bone of the endo-skeleton forms any 



