84. HYDROMORPHUS.—S85. DIMADES. 185 
contact with the anterior chin-shields, which are longer than the 
posterior. Scales in 15 rows. Ventrals 141-149 ; anal divided ; 
subeaudals 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 Rica. 
a-b. o (V. 149, 141; C. 65, 60). Cartago, Costa Rica. (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, J. c. p. 277, pl. —. fig. 3. 
Head much depressed, with broadly rounded snout. Nostrils 
directed upwards, the nasals separated by a pair of very small 
internasals ; prefrontal 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 
preocular between the supraocular and the loreal; two postoculars ; 
temporals 142; six upper labials, third bordering the eye; four 
lower labials in contact with the anterior chin-shields ; posterior 
chin-shieldssmall. Scalesin17rows. Ventrals 175; anal divided ; 
subeaudals 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. 
Pseudoeryx, part., Fitzing. N. Class. Rept. p. 29 (1826). 
Helicops, part., Wagler, Syst. Amph. p. 170 (1850). 
Homalopsis, part., Schleg. Phys. Serp. ii. p. 297 (1837). 
Dimades, part., Gray, Zool. Mise. p. 65 (1842). 
Dimades, Gray, Cat. Sn. p. 76 (1849). 
Colopisma, part., Dum. § Bibr. Erp. Gén. vii. p. 836 (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, 
