NORTH AMERICAN BATRACHIA AND REPTILIA. 27 



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, ])artly occujiying the excavated maxillary Crutalidd'. 



B. Maxilhuy 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 hypopophyses bifid. 



Elapidai. 



y. Maxillary produced to premaxillary, bearing solid 

 teeth; coronoid bone wanting Colubrida. 



x\rtificial Synopsis of Families. 



A. Sub-caudal scutella? entire; head very distinct from body. 



Crotalidw. 



B. Sub-caudal scutellaj bifid. 



X. Fostorb itals wanti ng; head continuous with body. -^"^^ 



~ ElapidiU. 



y. Fostorbitals present ; head variable Colubridai. 



Family CFtOTALID.E. 



A. Top of head scaled; tail terminated in a rattle. 



Crotahts. 



B. Toj) of head covered with symmetrical plates. 



a. Tail terminated in rattles Caudisona. 



h. Tail terminated in a horny point Ancistrodon. 



Genus Crotalus, Linn. 



1. C. horrldus^ 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 Austroriparian regions. 



2. C. adamanteus^ subsp. adamanteuSy (Beau v.) Cope. 

 Diamond Rattlesnake. Muzzle, marginal shields, and rostral, 



