228 



TROPICAL MEDICINE AND HYGIENE 



bones. The only teeth present are two or three in each 

 maxilla. 



In Calcutta, when water was supplied on the inter- 

 mittent system, it used to be not uncommon, at certain 

 seasons, for a small species of Typhlops to creep, somehow 

 or other, into the mains, and eventually to be discharged 

 in the efflux from taps, to the consternation of the house- 

 holder. 



(2) Glauconiidce. In form, external appearance, and 

 habits these snakes resemble Typhlopidat, with which 

 they also agree in most of their skeletal characters, 

 differing in the form of the upper jaw, and in having 

 teeth only in the mandible. It is a small family of about 

 thirty species, found for the most part in Africa and 

 Tropical America, but occurring also in Southern Asia. 



cor. 



FIG. 97. 



(3) Boiidce (Boas and Pythons). This family includes 

 about seventy species, some of which attain a length 

 of 30 ft., and are of formidable strength, being able to 

 overpower and crush large prey. They are found in 

 all warm parts of the world, one species ranging into 

 South-eastern Europe. Apart from all hidden differences 

 of structure, they can be distinguished from any 

 venomous land-snake by their ventral shields, which, 

 though enlarged, are of moderate size, and do not extend 

 to the flanks. As Major Wall expresses it, if a Boiid 

 snake be placed back downwards and belly upwards, at 

 least one complete row probably two or three rows 

 of the small scales of the flanks will be seen on either 

 side of the ventral shields in that position. As regards 

 skeletal differences, the Boiidce have vestiges of a pelvis 



