REPTILIA 225 



MODERN REPTILES 



The following list of diagnostic characters, which should be com- 

 pared with a similar list already given for Amphibia, is taken from 

 Gadow: 



CHARACTERS OF REPTILIA 



(D The vertebrae are gastrocentrous. 



fzJThe skull articulates with the atlas by one condyle, which is 

 formed mainly by the basioccipital. 



3. The mandible consists of many pieces and articulates with the 



cranium through the quadrate bones. 



4. There is an auditory columellar apparatus fitting into the fe- 



nestra ovalis. 



5. The limbs are of the tetrapodous pentadactyl type. 



6. There is an intracranial hypoglossal nerve. 



7. The ribs form a true sternum. 



8. The ilio-sacral connection is post-acetabular. 



9. The skin is covered (a) with scales, but (b) neither with feathers 



nor with hairs; and there is a great paucity of glands. 

 JoReptiles are 



11. The red blood-corpuscles are nucleated, biconvex and oval. 

 12._ The heart is divided into two atria and an incompletely divided 



ventricle. It has no conus, but semilunar valves exist at the 



base of the tripartite aortic trunk. 



13. The right and left aortic arches are c6mplete and remain func- 

 .-""-^ 



tional. - Jjf*^*' 



Respiration is effected by lungs; and. "gills are entirely absent 

 even during embryonic life. 



Lateral sense organs are absent. 



"he kidneys have no nephrostomes. Each kidney has one sep- 

 arate ureter. 



17. There is always a typical cloaca. 



18. The eggs are meroblastic. 



19. Fertilization is internal, and is effected, with the single exception 

 /V. of Sphenodon, by means of copulatory organs. 



I 20.J An amnion and an allantois are formed during development. 

 Numbers 1, 2, 3, 7, 8, 14, 16, 18, 20 separate the reptiles from 

 the Amphibia. 



