290 PHILOSOPHY OF ZOOLOGY. 



b. Serpents destitute of a third eye-lid. 



The serpents of this division are Ukewise destitute of all 

 vestiges of sternum, pelvis, or shoidder-bones ; neither do 

 the ribs unite to complete the circle. 



(a.) Body covered with scales. 



Scales in rings. 



38. Amphisb^na. Scales quadrangular, and^disposed in 

 circular bands round the body. Before the vent, there is a 

 vow of perforated tubercles, tlie openings of excretory 

 ducts. Oviparous. A.fullginosa. 



Scales imbricated. 



39. Typhlops. Scales small and placed in an imbricat- 

 ed order. Snout depressed and produced. Tongue long 

 and forked. T. lumbricalis. 



40. ToRTRrx. Ventral scales slightly enlarged. Tongue 

 thick and short. T. scytale. 



(6.) Body uniformly covered with tubercles. 



41. AcRocHORDUs. The tubercles may be viewed as mo- 

 difications of scales. They have each three ridges. The 

 top of the head is fat, and covered by small imbricated 

 scales. A. Javenensis. 



B. Serpents with the Ventral and Dorsal Scales Dissimilar. 



The ventral scales of this division constitute those shields 

 or scutae which have been already described. The lower 

 jaw-bones are loosely connected, and the ossa quadrata have 

 a free motion on the skull, or are supported on cartilagi- 

 nous or osseous peduncles. iThe upper maxillaries are 

 likewise loosely connected with the skull and the intermaxil- 

 lary bones. This condition of the jaws increases greatly 

 the power of gaping, and enables the serpents to take into 



