190 REPTILIA: OPHIDIA. XXVIII. 



r. Postfrontals 2 pairs ; loral single ; prefrontals 4 or more (scales 25 to 



35; V. P. 200 to 250) PITUOPHIS, 283. 



rr. Postfrontals 1 pair ; nasals 2 ; posterior teeth rather larger ; vivipa- 

 rous (scales 19 to 21; V. P. 140 to 180). . . . EUTAINIA, 276. 

 qq. Dorsal scales not keeled, rather loosely imbricate ; head short (V. P. 



160 to 240). 

 s. Rostral plate not acute. 



t. Loral present (scales 21 to 25) OPHIBOLUS, 285. 



tt. Loral absent (scales 19) OSCEOLA, 286. 



ss. Rostral plate acute, the snout sharp-pointed (scales 19). 



CEMOPHORA, 287. 



ff. Rostral plate (at tip of snout) produced, recurved and keeled; dorsal 

 scales keeled; anal plate divided; head broad and short; some of the 

 posterior teeth enlarged (scales 23 to 27 ; V. P. 120 to 150). 



HETERODON, 288. 



The following purely artificial key may aid in finding the names 

 of specimens : 



I. Dorsal scales not keeled ; anal plate bifid. 



a. Scales 13; V. P. about 130; color brownish . CARPHOPHIOPS, 269. 

 aa. Scales 15 to 17. 



d. Ventral plates about 120 ; brownish VIRGINIA, 271. 



bb. V. P. about 140. 



c. Blackish, with yellow collar. DIADOPHIS, 284. 



cc. Green; no collar LIOPELTIS, 281. 



bbb. V. P. about 185; blue-black, young blotched. BASCANION, 282. 

 aaa. Scales 19; V. P. about 180. 



d. Blue-black with three red lines ABASTOR, 270. 



dd. Blue-black with square red spots on sides. . . FARANCIA, 272. 

 aaaa. Scales 25 to 29 (median dorsal scales faintly keeled). 



COLUBER, 279. 



II. Dorsal scales not at all keeled; anal plate entire. 

 e. V. P. about 170 to 205; snout not sharp. 



/. Scales 19; red, black-banded OSCEOLA, 286. 



ff. Scales 21 to 25; black, brown or red, mostly variegated. 



OPHIBOLUS, 285. 

 ee. V. P. 160 to 170; scales, 19; snout sharp; red with black rings. 



CEMOPHORA, 287. 



III. Dorsal scales more or less keeled ; anal plate entire. 



g. Scales 19 to 21; V. P. about 155; striped . . . EUTAINIA, 276. 

 gy. Scales 25 to 35; V. P. about 220; blotched . . PITUOPHIS, 283. 



IV. Dorsal scales keeled ; anal plate bifid. 



h. Scales 15 to 17. 



i. Tail about J of length; V. P. 155; green. . . CYCLOPHIS, 280. 

 ft*. Tail not J of length ; brownish. 



j. Loral absent STORERIA, 274. 



jj. Loral present HALDEA, 273. 



hh. Scales 19 to 21. 

 k. V. P. about 135; blotched. .... TROPIDOCLONIUM, 275. 



