in the Collection of the British Museum. 91 



where snakes with simple subcaudals are more common than 

 anywhere else, there exist Ophidians which offer exceptions to 

 the general rule. In my last paper on Ophidians (Ann. Nat. 

 Hist. 1863, p. 363) I have made the remark that Reinhardt's 

 typical specimen of Atractaspis irregularis is described as having 

 scutella, whilst all the following writers attribute simple scuta to 

 this species. A specimen which Dr. Welwitsch brought from 

 Angola has the five anterior subcaudals entire, and the posterior 

 seventeen divided ; so that the character of simple subcaudals is 

 evidently subject to variation in the genus Atractaspis. Bibron 

 has made a similar observation in Leptodira rufescens, which 

 induced him to name the genus which he founded upon it 

 Heterurus. Therefore there is no reason why I should not con- 

 sider the specimen mentioned above as identical with Polemon 

 Barthii. 



Thus the question arises whether Uriechis, Peters, Microsoma, 

 Jan,= Urobelus, Ehrdt., Polemon, Jan, and Miodon,J)um., should 

 not be referred to one and the same genus. Peters thinks that 

 Polemon is a good genus, characterized by the articulation of the 

 maxillary and os pterygoideum externum by means of a double 

 process ; but the materials are at present much too scanty to 

 decide whether this character by itself is of generic value or not. 

 Nay, when we consider that only a few examples of those snakes 

 have been examined, that several of them are young, that Jan's 

 assertion of Microsoma having a simple nasal shield is contra- 

 dicted by Reinhardt, who found two in Ur obelus, we are justified 

 in recommending caution as regards the adoption of the several 

 species which have been proposed as distinct. 



Oligodon Waandersii. 



Scales in fifteen rows; ventrals 151, anal bifid, subcaudals 28. 

 Upper labials six, the third and fourth entering the orbit ; one 

 prse-, two post-oculars ; temporals 1 + 2. Upper parts brownish 

 olive, with pairs of yellowish spots, edged with blackish, along 

 the back ; head and neck with the markings characteristic of 

 this genus. Lower parts uniform white. 



The young has the spots more distinct, of a bright yellow 

 colour j there are about twelve pairs from the nape to the ex- 

 tremity of the tail. 



We have received two specimens from Dr. Bleeker : the larger 

 is 84 inches long, and has been named by him Rhabdion Waan- 

 dersii-, the younger, 4 inches long, R. cruciatum. They are 

 from Boni. 



Simotes vertebralis. 



Scales in fifteen rows. Upper labials seven, the third and 

 fourth entering the orbit ; loreal square ; one ante-, two post- 



