AND BATRACHIANS OF BARBAllT. 147 



The three species described below may be distinguished as follows : — 



Scales perfectly smootli, in 25 rows ; usually one labial entering the eye ; a pair 



of internasals and a pair of prefrontals 1. algirus. 



Scales perfectly smooth, in 27 (rarely 25 or 29) rows; usually no labial entering 



the eye j a pair of internasals and a pair of prsefrontals 2. hippocrepis. 



Scales more or less distinctly keeled, in 25 to 33 rows; no labial entering the 



eye ; usually three or more prtefrontals ; anal entire ........ 3. diadema. 



1. Zamenis algieus, Jan, 1863. 

 Z . florulentus , Gervais. 



Scales smooth, in 25 rows. One prfeocular, with a subocnlar below; two post- 

 oculars and a subocular; temporals 2 4-3 ; nine upper labials, rarely ten, fifth or sixth 

 usually entering the eye, but sometimes separated by an additional subocular. Yentrals 

 214 to 232; anal divided, rarely entire; subcaudals 92 to 100. Pale olive, yellowish 

 brown, or greyish above, with three alternating series of darker transverse bars, and a 

 series of dark spots along each side of the belly ; a more or less distinct blackish 

 crescentic band on the nape, extending to the sides of the throat ; a blackish spot 

 below the eye ; lower parts white. Young specimens may have the head entirely 

 black above. 



Total length 940 millim., tail 230. 



This species appears to be restricted to the Algerian and Tunisian Sahara. M. 

 Lataste obtained specimens in Algeria at Biskra, Laghouat, between Bou-Saada and 

 Biskra, and in Tunisia at Cabes, Raz-el-Oued, A'in-Zerig, Hadedj, Djebel Domeur, 

 Djerba Island, Tozeur, Ferriana, Gafsa ; and M. Valery-Mayet on Kerkenna, and at 

 Djebel Berda and Madjoura; specimens were obtained on the Tunisian Chotts by 

 Dr. Andre. 



Of 14 examples examined by M. Lataste, all have 25 rows of scales ; two have the 

 anal single. In 22 out of 28 cases the fifth labial enters the eye, in two cases the 

 sixth, in four the eye is completely separated from the labials by suboculars. 



Figure: Jan, Icon. Gen. Ophid. livr. 48, pi. iv. fig. 2. 



2. Zamenis hippocrepis, Linnseus, 1766. 



Scales smooth, in 25 to 29 rows, usually 27. One or two pi-seoculars ; two post- 

 oculars ; a series of three or four suboculars usually completely separates the eye from 

 the labials; temporals 2-1-3 or 3-1-3; eight or nine (rarely ten) upper labials, fifth or 

 sixth very rarely entering the eye. Ventrals 222 to 248 ; anal divided, rarely entire ; 

 subcaudals 79 to 107. Brown, reddish, yellow, or pale olive above, with a dorsal series 

 of large dark brown, black-edged rhomboidal spots, on each side of which is a series of 

 smaller alternating spots ; these spots may be black and so large as to reduce the 

 ground-colour to a mere chain or series of X's of pale colour; a dark cross-band 

 between the eyes, and a /\- ov horseshoe-shaped band on the back of the head, wliich 



