in the CuUection of the British Museum. 423 



posterior edge of whicli is rather irregular ; loreal as high as 

 long ; two pr^oculars, the upper of which contributes to the 

 canthus rostralis, extending to the upper side of the head, but 

 not by some distance reaching the vertical ; two postoculars ; 

 eight upper labials, the fifth onlj entering the orbit ; temporal 

 shields small, irregular. 



The median lower labial shield is extremely narrow ; the 

 chin-shields of nearly the same length, the anterior in contact 

 with four or five labials. 



Greyish olive ; many of the scales, especially on the hinder 

 part of the trunk, with a dark or blackish dot, a blackish 

 streak through the eye ; lower parts nearly uniform whitish. 



A single specimen has been sent by Dr. Kirk from Zanzibar. 

 It is 15 inches long ; length of the head 65 lines, of the tail 

 4 inches. 



RJiagerrhis tritceniata. PI. XIX. figs. H. 



I have been in some doubt as regards the systematic posi- 

 tion of this snake. Although it evidently belongs to the group 

 of Psammopliids, it does not perfectly agree with any of the 

 genera. Having the coloration of a true Psammoiyhis^ it difiers 

 from the species of this genus in its dentition, in which cha- 

 racter it agrees with Rhagerrhis ; but the rostral shield is not 

 so much produced — scarcely more than in Ccelopeltisj from 

 which it differs in the structure of the scales. 



Head rather short, scarcely distinct from neck ; body and 

 tail moderately slender. Eye of moderate size ; rostral shield 

 as high as long, extending to the upper surface of the head, 

 slightly advancing between the anterior frontals ; anterior 

 frontals not very much smaller than posterior ; vertical naiTOw, 

 rather longer than the snout, and conspicuously longer than 

 the occipitals, which are obliquely truncated behind ; two 

 nasals ; loreal square ; prseorbital single, sliglitly concave, not 

 quite reaching the vertical ; two postoculars ; eight upper 

 labial shields, the fourth and fifth entering the orbit ; tempo- 

 rals 2 + 3 + 4; two pairs of chin-shields, nearly equal in 

 length. 



Scales smooth, much imbricate, in seventeen rows, with a 

 small apical groove. Ventrals 161 ; anal bifid ; subcaudals 61. 



Brownish olive, with three dark-brown bands edged with 

 black. The median band occupies the vertebral series and the 

 halves of the adjoining series of scales, a white line running 

 along its middle ; this band commences immediately behind 

 the occipitals, and terminates in the anterior part of the tail. 

 The lateral band runs along the third and fourth outer series 

 and the halves of the adjoining series of scales, commencing 



