or THE COLD-BLOODED VERTEB^ATA. 219 



'Two occipital condyles. Teeth presenting a peculiar complex 



„ I arrangement of the cement .... Ord. LABYBiXTHODOif tia. 



One occipital condyle. Limbs natatory, with more tlaan five 



digits. Orbit very large Orel. Ichthtopteetoia. 



(Two occipital condyles. Pleurapophyses short and straight. 

 No scales or scutes. Larvse with gills . . Ord. Batrachia. 

 One occipital condyle. Larvae without gills 5. 



{Body covered with a double shield, formed of both the exo- 

 skeleton and endo-skeletou Ord. Chelonia. 

 Dermal armour, wlien present, formed wholly of the exo-skele- 

 ton, and never presenting the form of a double shield. ... 6. 



(Limbs not visible. No sacrum. Vertebras very numerous, with 

 a single transverse process on each side . . Ord. Ophidia. 

 Limbs present, with not more than five digits 7. 



{Anterior limbs formed for flight. Bones light, hollow, with 

 air-cells OrS. Pterosaurta. 

 Limbs ambulatory or natatory 8. 



o J Sacral vertebrae never exceeding two 9. 



\ Sacral vertebrae three or more 11. 



r Eibs bifurcate. One external nostril. Anterior trunk- vertebrae 

 „ J Avith two transverse processes. Skin protected by bony 



1 scales Ord. Crocodilia*. 



[ Eibs with simple heads. Two external nostrils 10. 



'Vertebrae flat, or somewliat biconcave. Limbs natatory. 



Ord. Saueoptebygii. 



Vertebrae, in most, procoelian, with a single transverse process 



on each side. Limbs ambulatory .... Ord, Lacebtilia. 



{Sacral vertebrae three. Teeth with compressed crowns ; sharp, 

 serrate ; in distinct sockets. Vertebrae biconcave. 

 Ord. Thecodontia. 

 Sacral vertebrae more than three 12, 



(Vertebrae biconcave. Teeth absent or represented by a pair 

 of tusks Ord. Akomodontia. 

 Vertebrae flat or concavo-convex. Limbs ambulatory, long 

 and strong. Teeth numerous Ord. Dinosaubia. 



Professor Owen, on the same occasion, gave it as his opinion 

 that the Pishes, Amphibians, and true Eeptiles ought properly to 

 be united into one class, for which he proposed the title of Haemato- 

 crya. AU the various forms cited in the above Table were re- 

 garded, under the general denomination of Eeptiles, as a sub-class 

 of this great division. 



Here two propositions are enunciated which call for the adop- 

 * Of this group there arc three sub-ordersi, Amphicoelia, Opistlwceelia, and 

 Procoelia. 



15* 



10 < 



