VERTEBEATA 



81 



The Peropoda are believed to be the most primitive 

 snakes, from which the other divisions have been derived. 

 The line to the Proteroglypha and Solenoglypha is an as- 

 cending one, while that to the Tortricina and Catodonta is 

 a descending one. 



The families embraced by these superfamilies are as fol- 

 lows : 



Catodonta ; Stenostomidse. 



Epanodonta ; Typhlopidse. 



Tortricina ; Tortricidse, Uropeltidfe. 



Colubroidea ; (Peropoda) Pythonidse, Boidse (Fig. 29), Char- 



inidse, Ungualiidse; (Aglyphodonta), Xenopeltidse (Fig. 



28), Acrochordidse, Nothopidse, Colubridse ; (Opistho- 



glypha) Dipsadidse ; (Proteroglypha), Elopida;, Naji- 



dse, Dendraspididse, Hydrophidse. 

 Solenoglypha; Causidse, Atractaspididse, Viperidffi, Crotali- 



dae. 



The paleontology of the snakes is very imperfectly known. 

 The oldest known genus, Symoliopsis Sauv., from the Neo- 

 comian of France, may be either one of the Catodonta or 

 Epanodonta. The oldest forms of Asinea (harmless snakes) 

 are Pythonidse and Boidse ; they occur in both continents. 



Fie. 29.— A, Palceovhis UUoralis Cope: B, P. halidanus Cope; vertebrm Both 

 from the Eocene of New Jersey. Cope. 



