16. TRETAJJORHINTJS. 281 



1. Hydrsethiops melanogaster. 



Hydi-fEtliiops melanogaster, Giinth. I. c. pi. iii. fip:- G. 



Helioops marginatus, Fischer, Oster-Prof/r. Ak. Gymn. JIamh. 1883, 



p. 11. 

 lineofasciatus, Sauvat/e, Bull. Sue. Zool. France, 1884, p. 203, 



pi. vi. fig. 3. 



Rostral as broad as deep, or a little broader, just visible from 

 -above and in contact with the internasal, which is triangular and 

 longer than broad ; frontal a little longer than broad, as long as 

 its distance from the end of the snout, shorter than the parietals ; 

 loreal a little longer than deep ; one prte- and two postoculars ; 

 temporals 1 + 2 or 1 + 3; ten or eleven upper labials, fifth and 

 sixth or sixth and seventh entering the eye ; three pairs of chin- 

 shields, the anterior in contact with five lower labials. Scales 

 more? or less strongly keeled, in 23 rows. Yentrals 143-154 ; anal 

 ■divided ; subcaudals 39-49. Dark olive-brown above, with five 

 more or less distinct series of alternating black spots ; a yellowish 

 stripe on each side, from the eye or the angle of the mouth along 

 the first and second rows of scales ; lower parts black. 



Total length 610 millim. ; tail 100. 



West Africa. 



.a-d. c? (V. 151 ; 0. 48) & $ (V. 147, Gaboon. (Types.) 



151, 149 ; C. 41, 39, 41). 

 e. 2 (V. 143; C. 48). Cameroons. 



16. TRETANORHINUS. 



Tretanorhiuiis, Dum. ^- Bibr. Erp. Gen. vii. p. 348 (1854) ; Jan, Arch. 



Zool. Anat. Phys. iii. 18(35, p. 254 ; Bocourt, Le Natitraliste, 1891, 



p. 121. 

 Helicops, part., Jan, I. c. p. 245. 



Maxillary teeth about 30, subequal ; mandibular teeth subequal. 

 Head slightly distinct from neck ; eye rather small, with round 

 pupil ; nostrils directed upwards, pierced bef^ween two nasals. 

 Body cylindrical ; scales striated and keeled, without apical pits, in 

 19 or 21 rows ; ventrals rounded. Tail moderate ; subcaudals in 

 two rows. Hypapophyses developed throughout the vertebral 

 column. 



Central America and Cuba. 



Spiojisis of the Species. 



Two pra^frontals ; posterior chin-shields 



separated from each other by scales ; 



scales in 19 rows 1. variabilis, p. 282. 



Two prajfrontals ; posterior chin-shields 



in contact with each other anteriorly ; 



scales in 21 rows 2. nigroluteus, p. 282. 



A single priB frontal ; posterior chin- shields 



in contact with each other anteriorly ; 



scales in 19 rows 3. mocquardii, p. 283. 



