Gloyd's Hump-nosed Viper

Adults grow to a total length of 30–35 cm (11+3⁄4–13+3⁄4 in). According to Wall (1921), the maximum recorded lengths are for a male of 38.7 cm (15+1⁄4 in) and a female of 38.1 cm (15.0 in). According to Deraniyagala (1955), the largest specimen in the Colombo museum was 39.2 cm (15+1⁄2 in) in total length with a tail measuring 5.9 cm (2+1⁄4 in). In general, the tail is 13-18% of total body length. The body is moderately slender, with a head that is conspicuously distinct from the neck. This species is distinguished from H. hypnale by a snout that has a strongly upturned tip. This is due to an extended rostral scale, which is immediately followed by a raised wart-like hump covered with 7-14 very small scales. Also, the hemipenes have clearly visible spines. The scalation includes 17 rows of dorsal scales at midbody that are weakly keeled or smooth, 124-142 ventral scales, and 33-41 subcaudal scales. The color pattern consists of a light brown to dark brown to pale olive ground color, flecked and mottled with darker tones. This is overlaid with a series of 17-26 dorsolateral suboval or subtriangular brown blotches that alternate or oppose each other middorsally. These blotches are 3-4 scales wide and extend down to the third scale row. The top of the head is brown, and usually lacks any pattern, except for a black postorbital stripe that extends to the neck.

Hypnale nepa is found in Sri Lanka throughout forested areas, from lowland rainforest to over 1,800 m (5,900 ft) altitude. The type locality given is "Africa." An obvious error, this was amended to "Sri Lanka" by Hoge and Romano-Hoge (1981).