TABLE 1. Morphological comparison between the type specimens of Tropidonotus nicobarensis, Prymnomiodon chalceus and literature data based on Thamnophis saurita. Data for Th. saurita originate from Rossman (1963) and Rossman et al. (1996). Data noted with an asterisk indicate the tails in specimens were broken or damaged. Data in parentheses indicate rare occurrences, whereas data in brackets indicate data from literature sources.

Character	Tropidonotus nicobarensis	Prymnomiodon chalceus	Thamnophis saurita
Muzzle Length/Frontal Length	0.510	0.610	usually less than 0.700
Loreal	1/1	1/1	1/1
Preoculars	1/1	1/1	1/1
Postoculars	3/3	3/3	3 (2, 4, 5)
Supralabials	8/7	8/7	7–8 (6, 9)
Supralabials contacting eye	4+5/3+4	4+5/3+4	3+4–4+5
Anterior Temporals	1/1	1/1	1 (2)
Posterior Temporals	2/2	2/2	2 (1, 3, 4)
Infralabials	10/10	9/10	9–10 (7, 8, 11, 12)
Infralabials contating upper chin shields	5/5	4/5	4–5
Anterior dorsal scales	19	19	19 (17, 18)
Midbody dorsal scales	19	19	19 (17, 18)
Posterior dorsal scales	17	17	17 (16)
Ventrals	160	152	143–177
Subcaudals	88 [120] *	24 *	94–136
Cloacal plate	Undivided	Undivided	Undivided
Maxillary teeth	[25 or 24]	31	27–34
Vertebral stripe	Present, dark edges	Present, dark edges	Present, dark edges
Position of lateral stripe	3rd and 4th dorsal scale rows	3rd and 4th dorsal scale rows	3rd, 4th dorsal scale rows
Width of lateral stripes on each dorsal scale	0.5	0.5	0.5
Temporal streak	Present	Present	Present