COLUBRID.-E. — CX. 189 



dd. Nasal plates 2, the nostril between them; a loral plate; no preocu- 



lar; (scales 15 or 17, V. P. 115 to 125). . . . Virginia, 271. 



cc. Prefrontal single; no preocular; nasal single ; (scales 19; V. P. 170 to 



205) Farancia, 272. 



an. Head more or less distinct from the body which is not specially rigid 



(Coronellinm, 1 Colubrina, Homalopsiiue). 

 f. Rostral plate normal, not recurved nor keeled. 

 g. Anal plate divided ; head not very short. 

 h. Dorsal scales keeled more or less. 

 i. Nasal plates 2, the nostril between them. 

 j. Prefrontals 2. 



/.-. Loral plate pre: ent. 



I. Scales on back and sides all keeled (ventral plates 130 to 170). 

 m. Posterior teeth not longer (scales 19 to 2i). . Regina, 277. 

 mm. Posterior teeth longer (scales 23 to 31). 



Tropidonotus, 278. 



II. Scales on sides not keeled; those on back often with the 



keels obscure (V. P. 200 to 270 ; scales 25 to 29). 



Coluber, 279. 

 Ik. Loral plate absent (scales 15 to 17; V. P. 125 to 130). 



Storeria, 274. 

 jj. Prefrontal single : nasals 2 ; loral present ; no preocular (scales 17 ; 

 V. P. 120 to 130); body slender, the head distinct. 



Haldea, 273. 

 ii. Nasal single, pierced by the nostril ; loral plate present. 



n. Nasal plate grooved; tail short (scales 19; V. P. 130 to 



1-10) Troi'idocloxium, 275. 



rare. Nasal plate not grooved below nostril ; tail very long, 

 about J of length (scales 17; V. P. 150 to 160). 



Cyclophis, 280. 

 h h. Dorsal scales not keeled. 



o. Nasal single, pierced by the nostril; loral present; tail 

 long (scales 15 ; V. P. 125 to 140). Ltoi-kltis, 281. 

 oo. Nasal plates 2. the nostril between them; loral pres- 

 ent ; preoculars 2. 

 p. Head depressed ; preoculars nearly equal in size 

 (scales 15 to 17; V. P. 140 to 200 or more). 



Diadophis, 284. 



pp. Head not depressed; upper preocular much tin; 



larger; lower sometimes wanting ; (scales 17; V. 



P. 170 to 210) Bascanion, 282. 



gg. Anal plate entire. 



q. Dorsal scales all or part of them keeled ; head 

 rather long. 



1 These three sub-families are so vaguely bounded that I cannot use their distinc- 

 tive characters in the key. Professor Cope gives the following definitions : — 



Homalopsinw. (Genera 273 to 27S.) " Hypapophyses spinous to caudal region; an- 

 terior teeth not enlarged; body not slender; head distinct." 



Colubrinrc. (Genera _'7:< t" 2^3.) Head more distinct and elongate; body and tail 

 longer; teeth entire, not longer in front. 



' (Genera 2S4 to 288.) Head slightly distinct, short; teeth entire, 



not enlarged in front. 



