392 GEOGRAPHICAL ZOOLOGY. [part iv. 



(listribution. Their head-quarters is the Ethiopian region, 

 which contains more tlian ]ialf the known genera and species, 

 most of which are found in South Africa and several in Mada- 

 gascar. Next to Africa the largest number of genera and species 

 are found in Mexico and Central America,with a few in the Antilles, 

 South America, and California, and even as far north as British 

 Columbia. Three of the genera form a distinct sub-group — the 

 Glass Snakes, — the four species composing it being located in 

 North Africa, North America, South-eastern Europe, and the 

 Khasya Hills. 



The prominent fact in the distribution of this family is, that 

 the mass of the genera and species form two groups, one in South 

 Africa, the other in Mexico, — countries between which it would 

 be difficult to imagine any means of communication. We have 

 here, probably, an example of a once much more extensive group, 

 widely distributed over the globe, and which has continued to 

 maintain itself only in those districts especially adapted to its 

 peculiar type of organization. This must undoubtedly have 

 been the case with the genus Fseudopus, whose two species now 

 inhabit South-eastern Europe and the Khasya Hills in Assam 

 respectively. 



The genera are, — Cordylits, Pseudocordylus, Platysaurus, 

 Cordylosaurus, Pleurostrichus, and Saurophis, confined to South 

 Africa ; Zonurus, South and East Africa and Madagascar ; Ger- 

 rhosaurus, ranges over the whole Ethiopian region ; Cicigna is 

 confined to Madagascar; Gerrhonotus (22 sp.), ranges from 

 British Columbia, California, and Texas, to Cuba and South 

 America, but is most abundant in Mexico and Central America ; 

 Ahronia and Barissia, are two genera of doubtful distinctness, 

 peculiar to Mexico ; Ophisaurus (the Glass Snake) is found in 

 the Southern United States as far as Virginia ; the allied genus 

 Hyalosaurus in North Africa ; and Pseudopus, as above stated, 

 in South-east Europe and the Khasya Hills. 



