CROCODILIAN^, LIZARDS, AND SNAKES, 201 



II. Petrosal produced anterior to semicircular canal, not articulating above with 



parietal. 

 a. Clavicle proxiraally expanded; olfactory lobe underarched by frontal. 



Tongue papillose or smooth ; hemipenis calyculate Nyctisaura. 



aa. Clavicle proximately simple ; olfactory lobes underarched by frontaL 

 VertebriBamphico'lous; nosupratemporalarch ; tonguepapillose.UROPLATOiDEA. 

 Vertebra; proccelous; a supratemporal arch ; interclavicle anchor-shaped; tongue 



smooth ; hemipenis flounced Thecaglossa. 



Vertebrte proccelous; no supratemporal arch; tongue papillose; interclavicle 



simple; hemipenis flounced Helodermatoidea. 



a a a Clavicle simple proximally, olfactory lobes not underarched by frontal. 



Interclavicle cruciform; tongue papillose; hemipenis flounced Diploglossa. 



a a a a Clavicle proximally expanded, olfactory lobes not underarched. 

 Vertebra' procadous ; tongue scaly ; hemipenis flounced or plicate . . Leptoglossa. 



III. Petrosal produced anterior to the anterior semicircular canal, articulating above 



with the border of the parietal. 

 Olfactory lobes underarched by frontals; no supratemporal arch, nor scapular 

 arch, nor sternum ; cervical and caudal intercentra coossifled 

 with the middles of the centra Annulatj . 



The extiuct family of the Dolicliosauridse probably represents another 

 super-family, but its characters are not well known. It is so far only 

 known from the Cretaceous bed of Europe. The genus DoUchosaurus 

 (Owen) is remarkable for the large number of cervical vertebrai, there 

 being not less than seventeen in the series. 



III. PHYLOGENETIG KELATIONS. 



The degradational tendencies of the Sauria have been already re- 

 ferred to, as especially exhibited in the reduction of the limbs. This 

 has been associated with a close adhesion to a life on the ground, and 

 ultimately with a life beneath the surface of the ground. Goincident- 

 ally with this habit there has taken place a reduction in the eflficiency 

 of the sense of sight. The eyelids have disappeared and the ejiidermis 

 has become thickened over the cornea, and has ultiinately assumed the 

 character of the eindermis of the other parts of the head and body. 

 The corium has in some cases closed over the orbit, so that total blind- 

 ness has resulted. 



These reductions are seen least in families and genera of arboreal 

 habits. No member of the Ehiptoglossa, Nyctisaura, Acrodonta, or 

 Iguania displays any of them. They are first seen to a limited degree 

 ill the Diploglossa, while they are very common in the Leptoglossa, and 

 universal in the Typhlophthalmi and Amphisbnenia. I give the follow- 

 ing table which displays at once the degradational series of the limbs 

 in the respective families in which it occurs. 1 also include some fusions 

 of cephalic dermal plates. 



