SNAKE FAUNA OF SOUTH AFRICA. 313 



Leptodira, Chamaetortiis, Amplorhinus, Trimerorhinus, Thelotor- 

 nis, Rhamphiophis , Dispholidus, Psamtnophis, Arnhlyodipsas, 

 Calanielaps, Xenocalamns , Macrelaps, and Aparallactus ; and 12 

 out of the fifteen are confined to tropical and South Africa. 



One of them, Leptodira, occurs also in tropical South America, 

 extending northwards as far as Texas ; Psamtnophis extends into 

 Southern Asia as far as Burmah ; and Tarhophis occurs through- 

 out tropical and N.E. Africa, S.E. Europe and S.W. Asia. 



According to Mocquard, four of the Madagascar genera have 

 the posterior hypapophyses distinctly developed (in the B.M. 

 Catalogue another genus (Eteirodipsas) is in the same category), 

 whereas only one genus (Pythonodipsas) out of 15 recorded from 

 South Africa has these processes. 



According to Mr. Boulenger in the B.M. Catalogue, the great 

 majority of the known Opisthoglyphous genera are characterised 

 by an absence of posterior hypapophyses ; and such processes 

 occur only in the above-mentioned Madagascar genera, one of 

 which has a representative in East Africa, in a genus peculiar to 

 the Comoro Islands, in one South African genus in a genus 

 peculiar to Socotra, and in a species peculiar to the Philippine 

 Islands. 



The monotypic Madagascar genus Mimophis, which is without 

 the processes, appears to be most closely related to Psammophis, 

 a genus whose headquarters is in Africa, with one or two outlying 

 members in India. These two genera, together with four others, 

 which all belong to the old world, are placed in a distinct sub- 

 family, the Psammophinae. 



The above facts rather suggest that the Opisthoglvpha are not 

 a natural group, but have been developed along parallel lines from 

 various genera of aglyphous snakes ; for whilst the great majority 

 of the Madagascar Colubridae agree together in the possession of 

 these processes, and therefore are probably genetically related, 

 there is nothing to suggest that all the ancestral opisthoglypha 

 elsewhere were similarly endowed. I must mention, however, tliat 

 according to Nils Rosen* the presence or absence of posterior 

 hypapophyses is by no means a constant character in some spe- 

 cies ; should this prove to be a fact of general application (which 

 I think is doubtful) the foregoing argument is of course invalid. 



RHACHIODONTINAE. 



This sub-family comprises only two species, Dasypeltis scabra, 

 distributed throughout tropical and Southern Africa, and D. 

 macrops, from Cameroon. 



ELAPINAE. 



The following genera occur in South Africa : Elapechis, Naia, 

 Sepedon, Aspidelaps, Homorelaps and Dendraspis ; these genera, 

 Naia only excepted, are peculiar to Tropical and South Africa. 

 The genus Naia occurs throughout Africa and Southern Asia, 

 extending to China and the Malay Archipelago. So far as can 



* A.M.N.H., 7, 16, p. 126. 



