84. HTDROMORPHCS. 85. DIMADES. 185 



contact witt the anterior chin-shields, which are longer than the 

 posterior. Scales in 15 rows. Ventrals 141-149 ; anal divided ; 

 Bubcauda,ls 60-65. Dark brown above, with five blackish longi- 

 tudinal lines ; a more or less distinct yellowish collar ; lateral scales 

 lighter in the centre ; labials yellowish, spotted with black ; lower 

 parts uniform whitish. 



Total length 290 millim. ; tail 77. 



Costa Eica. 



a-h. d (V. 149, 141 ; C. 65, 60). Cartage, Costa Eica. (Types.) 



84. HYDROMORPHUS. 

 Hydromorphus, Peters, Mon. Berl. Ac. 1859, p. 276. 



Maxillary short, with 14 teeth, which gradually increase in length 

 to the last; mandibular teeth subequal. Head scarcely distinct 

 from neck ; eye very small, with round pupil ; a single prefrontal ; 

 nostril directed upwards, in a single shield ; loreal entering the 

 eye. Body rather elongate, cylindrical ; scales smooth, in 17 rows ; 

 ventrals rounded. Tail short ; subcaudals in two rows. 



Central America. 



1. Hydromorphus concolor. 



Hydromorphus concolor, Peters, I. e. p. 277, pi. — . fig. 3. 



Head much depressed, with broadly rounded snout. Nostrils 

 directed upwards, the nasals separated by a pair of very small 

 internasals ; prisfrontal twice as broad as long ; frontal slightly 

 longer than broad, as long as its distance from the rostral, much 

 shorter than the parietals ; loreal twice as long as deep ; a small 

 prKocular between the supraocular and the loreal ; two postoculars ; 

 temporals 1 + 2; six upper labials, third bordering the eye ; four 

 lower labials in contact with the anterior chin-.shields ; posterior 

 chin-shields small. Scales in 17 rows. Ventrals 175 ; anal divided ; 

 subcaudals 31 . Dark greyish brown above ; sides and lower parts 

 paler, the scales and shields being partly yellowish. 



Total length 850 millim. ; tail 86. 



Costa Rica. 



85. DIMADES. •'«<^ / i •' /J "" 



Pseudoeryx, part., Fitzing. N. Class. Rept. p. 29 (1826). 

 Helicops, part., Wagler, Syst. Amph. p. 170 (1830). 

 Homalopsis, part., Schleg. Phys. Serp. ii. p. 297 (1837). 

 Dimades, part.. Gray, Zool. Misc. p. 65 (1842;. 

 Dimades, Gray, Cat. Sn.v- 76 (1849). 



Colopisma, part., Dum. ^ Bibr. Erp. Gen. vii. p. 336 (1854) ; Jan, 

 Arch. Zool. Anat. Phys. iii. 1865, p. 241. 



Maxillary teeth 15 to 17, gradually increasing in size ; man- 

 dibular teeth subequal. Head small, not distinct from neck ; eye 

 rather small, with round pupil ; nostril directed upwards, in a semi- 

 divided nasal; a single internasal; no loreal. Body cylindrical, 



