284 Dr. A. Giinther on some Species of Tree-Snakes. 



The species named were evidently most closely allied to one 

 another, and from the descriptions and figures alone it was 

 almost impossible to find out which of the differences were 

 of a really specific value ; hence, although, in the ' Catalogue of 

 Colubrine Snakes ' (p. 152), I could not hesitate to refer Ph. al- 

 bovariatus to its proper place as a synonym of A. irregularis, I 

 withheld my opinion as to Ph. semivariegalus and Chlorophis 

 heterodermus, of which I had seen no specimens, mistaking 

 altogether the Ph. natalensis, which I have since recognized. 



M. A. Dumeril was in a still more difficult position than 

 myself when he published his paper, " Reptiles et Poissons de 

 l'Afrique Occidentale " (Archiv. Mus. t. x.), having for exami- 

 nation only the A. irregularis in the collection of the Paris 

 Museum. Therefore we can hardly be surprised to find that, 

 in his opinion, the three species of Smith would be distinct from 

 A. irregularis, whilst Chlorophis heterodermus would be only a 

 synonym. 



In order to terminate this state of uncertainty, the attention 

 of travellers and collectors has been directed to these Snakes ; 

 and having brought together nearly 100 specimens, with the 

 localities whence they were obtained well marked, I have come 

 to the following conclusions : — 



1 . Coluber irregularis, Dendrophis Chenonii, and Philothamnus 

 albovariatus are synonyms of the same species, which is the 

 most common of all. 



2. Philothamnus semivariegalus, Ph. natalensis, and Chlo- 

 rophis heterodermus are distinct species. 



3. Ahcetulla hoplog aster and A. heterolepidota are two new 

 species. 



4. All these species are distinguished from one another by at 

 least two characters, which are constantly combined with each 

 other ; the number and shape of the temporal shields is subject 

 to some variation, not only within the limits of the same species, 

 but also on the two sides of the same individual. 



Synopsis of the Species. 



I. Ventral shields laterally keeled. 



a. Upper labials nine, three entering the orbit. 



a. Anal bifid; ventral shields 164— 1/7- ... A. irregularis. 



b. Anal entire; ventral shields 150-15/ .. A. heteroderma. 



c. Ventral shields 20/ ; trunk with black 



cross-bands anteriorly A. semivarieyata. 



B. Upper labials eight (seven). 



a. Two labials enter the orbit; ventral 



shields 151-168 A. natalensis. 



b. Three labials enter the orbit; ventral 



shields 187 A. heterolepidota. 



II. Ventral shields without a trace of lateral keels. 



Anal bifid A. hoplogaster. 



