190 REPTILIA: OPHIDIA. — XXVIII. 
r. Prefrontals 2 pairs; loral single; prefrontals 4 or more (scales 25 to 
35; V. P. 200 to 250), . . «© © © «© + © « PITUOPHIS, 283. 
rr. Prefrontals 1 pair; nasals 2; posterior teeth rather larger; vivipa- 
rous (scales 19 to 21; V. P. 140 to 180). . . THAMNOPHIS, 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). . . . . LAMPROPELTIS, 285. 
tt. Loral absent (scales 19) . . . . « « » + OSCEOLA, 286. 
ss. Rostral plate acute, the snout sharp-pointed (scales 19), 
CEMOPHORA, 287. 
Jf. 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 180; color brownish . CaRPHOPHIOPs, 269. 
aa. Scales 15 to 17. 
6. Ventral plates about 120; brownish. . . - ~ VIRGINIA, 271. 
bb. V. P. about 140. 
ce. Blackish, with yellow collar. « » « « » DIADOPHIS, 284, 
cc. Green; nocollar. . . . * . « Liope.tis, 281. 
bbb. V.P. about 185; blue-black, gine 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). 
CALLOPELTIS, 279. 
II. Dorsal scales not at all keeled; anal plate entire. 
e. V. P. about 170 to 205; snout not sharp. 
J. Scales 19; red, black-banded. sah <a + + OSCEOLA, 286. 
Jf. Scales ai to 25; black, brown, or red, mostly variegated. 
LAMPROPELTIS, 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... . THAMNoPHIs, 276. 
gg. Scales 25 to 35; V. P. about 220; blotched... . Prrvopuis, 283. 
IV. Dorsal scales keeled; anal plate bifid. 
ua _Scales 15 to 17. 
~ Tail about 4 of length; V. P. 155; green. . Opnxonrys, 280. 
. Tail not 4 of length; brownish. ~ 
% Loral absent. . . soe oe + ee » «6 STORERIA, 274. 
jj. Loral present. . - . 6 + «© © «© © © « » HALDEA, 273. 
hh. Scales 19 to 21. 
k. V.P. about 185; blotched. . . . . . . . CLONOPHIS, 275, 
