162 Dr. A. Gunther on a new Genus of West African Snakes, 



vertical is five-sided, with an obtuse anterior and an acute pos- 

 terior angle, and with the posterior sides longer than any of the 

 others. The occipitals taper posteriorly. The anterior nasal 

 is small and notched by the nostril; the posterior is evidently 

 formed by the united loreal and postnasal shields. One ante- 

 rior and one posterior ocular. Seven upper labial shields : the 

 first and second are small ; the third touches the postnasal, 

 prseorbital, and the eye ; the fourth below the orbit ; the fifth 

 touches the postocular, the sixth the occipital and slightly 

 the postocular, the seventh the temporal : there is another 

 scale-like shield behind the seventh labial, to which, however, 

 the cleft of the mouth does not extend. A single large temporal 

 shield is separated from the postocular by the intervening sixth 

 labial shield. The first pair of the lower labials form a suture 

 together behind the median one ; there are two pairs of chin- 

 shields of nearly equal size. The trunk is surrounded on every 

 part by fifteen rows of scales. There are 160 ventral and 44 

 subcaudal plates, all being entire. 



The upper parts are uniform greyish olive, or black after the 

 epidermis is detached. The lower side is uniform yellowish 

 olive, or white if the epidermis is lost. 



The total length is 19 inches, the cleft of the mouth being 

 one-third of an inch and the tail 2f . 



The specimen formed part of a collection of West African snakes 

 purchased of Mr. Rich for the British Museum, and containing 

 Coronella fuliginoides, Grayia* triangularis, Meizodon regularis, 

 Dipsadoboa unicolor, &c. 



Among the best-determined genera of Ophidians are those 

 distinguished by entire subcaudal plates. Out of fifteen genera 

 with which we are at present acquainted possessing this cha- 

 racter, no less than five are from Western Africa : namely Ela- 

 pops, belonging to the family Calamaridse ; Dipsadoboa [unicolor), 

 to the Dipsadidse ; Holuropholis, to the Lycodontidse ; and Atrac- 

 taspis, the type of a distinct family, to which perhaps Polemonf 

 may belong. This is a very remarkable feature of the Ophidian 

 fauna of Western Africa, in which it appears to be very different 

 from the southern parts of the Ethiopian region, where, accord- 

 ing to the present state of our knowledge, but a single snake 

 with the character above mentioned is found, viz. Atractaspis 



* The name of Heteronotus is inadmissible, it being used for a genus of 

 Lizards; see Gray, Catal. Lizards. 



t Provided that Polemon (of the venomous tooth of which we are not 

 yet informed whether it is externally grooved or perforated by an internal 

 channel) is a genus really different from Atractaspis. The genera which 

 have only a part of the subcaudals entire are not brought into the above 

 account. 



