2 VENOMOUS SNAKES AND THE PHENOMENA OF THEIR VENOMS 



ing out the Solenoglypha, which is also eurystomatous. Peropoda is not in 

 Dumeril's system, although a Eurystomata. 



Finally, Boulenger succeeded in formulating a more natural and rational 

 classification of these animals, which is accepted by most systematists as by 

 far the best proposed. His phylogenetic system stands as follows: 



g.Viperidce 



I. No ectopterygoid ; pterygoid not extending to quadrate or to mandible; no 

 supratemporal (squamosal); prefrontal forming a suture with 



nasal; coronoid present; vestiges of pelvis 



Maxillary vertical, loosely attached, toothed; mandible edentulous; a 



single pelvic bone Typhlopidee. 



Maxillary bordering mouth, forming a suture with premaxillary, [pre- 

 f rental and frontal, toothless; lower jaw toothed; pubis and 



ischium present, latter forming a symphysis Glauconiida. 



II. Ectopterygoid present; both jaws toothed. 



A. Coronoid present; prefrontal in contact with nasal. 



1. Vestiges of hind limbs; supratemporal (squamosal) present. 



Squamosal large, suspending quadrate Boidae. 



Squamosal small, intercalated in cranial wall IlysiidoR. 



2. No vestiges of limbs; squamosal absent Uropeltidce. 



B. Coronoid absent; squamosal present. 



1. Maxillary horizontal; pterygoid reaching quadrate or mandible. 



Prefrontal bone in contact with nasal Xenopeltidce. 



Prefrontal not in contact with nasal Colubrida. 



2. Maxillary horizontal; pterygoid not reaching quadrate or man- 



dible Amblycephalidce. 



3. Maxillary vertically erectile, perpendicularly to ectopterygoid; ptery- 



goid reaching quadrate or mandible Viperidee. 



Apart from these anatomical characters the following synopsis will serve 

 better for ordinary practical purposes: 



Typhlopidce: Eyes vestigial; no teeth in lower jaw; without enlarged ventral scales. 



Glauconiidce: Eyes vestigial; teeth restricted to lower jaw; without enlarged ventral scales. 



Uropeltidce: Eyes very small; head not distinct; ventral scales scarcely enlarged; tail 

 extremely short, ending obtusely and covered with peculiar scales. 



Ilysiida: Eyes functional and free; claw-like spurs of vestiges of the hind limbs on 

 each side of vent; ventral scales scarcely enlarged. 



BoidcR: Eyes functional and free; claw-like spurs of vestiges of hind limbs on each 

 side of vent; ventral scales transversely enlarged. 



Xenopeltida: Eyes free; no vestiges of limbs or of their girdles; maxillary typical, hori- 

 zontal, not separately movable, with a series of teeth; mandible toothed, but no 

 coronoid bone. Dentary movably attached to tip of articular bone of mandible; 

 skin beautifully iridescent. 



Amblycephalidce: Like the Xenopeltidae, but ends of pterygoids free, not reaching the 

 quadrates. No mental groove. 



Colubridce: Like the Xenopeltidae in main characters, but squamosal horizontally 

 elongated and movable; pterygoid reaches the quadrate. Median longitudinal 

 line between shields of chin. 



Viperidce: Eyes free; pair of poison fangs in front part of mouth, carried by the other- 

 wise toothless, much shortened, and vertically erectile maxillaries. Ventral scales 

 transversely enlarged. 



