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: 



Chaeacters op Reptilla. 



1. The vertebrae are gastrocentrous. 



2. The 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. 



10. Reptiles are poikilothermous. 



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 complete and remain func- 



tional. 



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



even during embryonic life. 



15. Lateral sense organs are absent. 



16. The 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 



of Sphenodon, by means of copulatory organs. 



20. A.n amnion and an allantois are formed during development. 



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

 the Amphibia. 



