128 Trans. Acad. Sci. of St. Louis. 



The anatomical characters which distinguish them consist chiefly 

 in the separate condition of the rami of the lower jaw in the snakes, 

 while they are solidly united in the lizards; in the total absence even 

 of vestiges of a pectoral arch in the snakes; and in the closing of the 

 brain case anteriorly in the latter. There are no external characters 

 which will in all cases separate a snake from a limbless lizard, ex- 

 cept that in the latter the tongue is not retractile into a basal sheath, 

 while in most cases they possess distinct eyelids and ear-openings, 

 both wanting in the snakes. (Stejneger.) 



Suborder SAURIA. 



Body elongated and covered with numerous small imbricated scales. 

 Four limbs (rarely wanting). Shoulder girdle always present. Bye- 

 lids and external organs of hearing present. Jaws with teeth set in a 

 continuous groove; jaws not dilatable. Heart with three chambers. 

 Urinary bladder present. Oviparous, with a few exceptions. (Garman.) 



Key to the Families Represented in Missouri. 



Tongue not bifid. Legs four. Scales imbricated, carinated above. 

 A fold of the skin on each side of the neck. Proximal end of 

 clavicle simple. Iguanidae. 



Tongue deeply bifid, with an ensheathing base. Legs wanting, or 

 with a pair of rudimentary hind legs. Body serpenti-form. A 

 lateral longitudinal groove. Proximal end of clavicle simple. 



Anguidae. 



Tongue bifid, but with no ensheathing base. Legs four. Two 

 transverse subgular folds of skin. Scales granular above, large 

 below. Premaxillary single. Clavicle dilated at proximal end. 



Teiidae. 



Tongue notched at the tip. Legs four. No transverse subgular 

 folds. Scales smooth and about uniform in size above and be- 

 low. Premaxillary double. Proximal end of clavicle simple. 



Scincidae. 



Family Iguanidae. 



Tongue short, thick, fleshy, but slightly free in front, scarcely bifid. 

 Teeth attached to the inner face of the jaws, pleurodont. Femoral 

 pores present or absent. Premaxillary single. Clavicle with simple 

 proximal ends. Mesosternum anchor-shaped. A xiphisternal fon- 

 tanel present. Abdominal ribs generally wanting. (Garman.) 



