NORTH AMERICAN BATRACIIIA AND REPTILIA . 
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Order OPHIDIA. 
Synopsis of Families. 
A. Maxillary bone vertical; fangs erectile, perforated, and 
not grooved externally ; a deep fossa on each side of head behind 
nostril, partly occupying the excavated maxillary Grotalidce. 
B. Maxillary bone horizontal, not excavated; rudimentary 
extremities none. 
x. Maxillary with a permanently erect, perforated, and 
usually grooved tooth; neural spines and pleura- 
pophyses short ; caudal liypopophyses bifid. 
Elapidce. 
y. Maxillary produced to premaxillary, bearing solid 
teeth ; coronoid bone wanting Golubridoi. 
Artificial Synopsis of Families. 
A. Sub-caudal scutellse entire ; head very distinct from body. 
Grotalidce. 
B. Sub-caudal scutellse bifid. 
x. Postorbitals wanting; head continuous with body. 
Elajpidce. 
y. Postorbitals present ; head variable ..... Golubridce. 
Family CROTALIDAL 
A. Top of head scaled ; tail terminated in a rattle. 
Grotalus. 
B. Top of head covered with symmetrical plates. 
a. Tail terminated in rattles Gaudisona. 
b. Tail terminated in a horny point Ancistrodon. 
Genus Crotalus, Linn. 
1. G. horridus , Linn. Northern Rattlesnake. Muzzle 
covered above with small plates or numerous scales; two mar- 
ginal shields between superciliary and rostral; rostral high, 
narrow, cuneiform; scales 23-25 rows, all carinate ; 12-14 labials ; 
two rows of scales between them and the orbit; a light line 
from superciliary plate to angle of mouth; on body two series 
of brown dorsal rhombs, which are confluent, except on the 
anterior part, forming transverse zigzag blotches; tail black; 
general color sulphur-brown of various shades; G. 165-170. 
Eastern and Austrori parian regions. 
2. G. adamanteus , subsp. adamant eus, (Beauv.) Cope. 
Diamond Rattlesnake. Muzzle, marginal shields, and rostral, 
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