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 imperfectly divided ventricle. It has no conus, but semilunar valves exist at the base of the tripartite aortic trunk.
13. The right and left aortic arch are complete and remain functional.
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 separate ureter.
17. There is always a typical cloaca.
18. The eggs are meroblastic.