U6 SYXOPSES AND DESCRIPTIOXS. 



tions, anterior large, posterior narrow. Generally two small loreals, some- 

 times more. Eye rather large. Two anteoi'bitals ; lower small, triangular, 

 toucliing the orbit in a sharp angle. Sub and postorbitals five or six, small, 

 anterior separated from the labials by one or two scales. Cheek scales 

 larger, smooth. Labials 12 — 16, first and fifth lai'ger. Infralabials 13 — 18. 

 A pair of large submentals. Scales keeled, in 23 — 25 rows, outer broad, 

 nearly or quite smooth. Ventrals 165 — 175-f 19 — 25. 



Brownish yellow to yellowish-brown or black. A dorsal and two lateral 

 series of light-edged black spots, which become confluent into transverse 

 bands posteriorly. Anteriorly the spots appear as if formed of sections of 

 a zigzag band. Tail banded in young, black in adults. The young have 

 the spots lighter in the center; a pair of elongate spots extend fi'om the 

 back of the head on the nec"k; a band extends fi'om the eye across the 

 angle of the mouth, a series of small oblong spots on the flank alternates 

 with those of the other series, and occasionally the anterior spots of the 

 dorsal series are bifid. There is great variation in shape and size of spots 

 and in depth of ground color; some are almost black, others are of a sul- 

 phur yellow. The sides of the rattle are nearly parallel in old specimens, 

 and commonly there is a secondary groove or series of indentations between 

 the median groove and the U2:»per edge. In a specimen of a total length 

 of fifty-four inches the tail is less than four. Hab. Massachusetts to 

 Mississippi. 



Ckotalus cerastes. 



Ealhwell, 1854, Pr. Ac. N. Sc., Phil., 95. 



Small ; head small, not angulate, crown tubercular. A single large nasal. 

 Lateral edge of supraciliary produced above the eye so as to resemble a 

 horn. Labials 11—13. Rows of scales 21—23. Ventrals 146+17. 



Yellowish, with a dorsal series of indistinct brown blotches, below which 

 on the flanks are irregular series of brown dots. A brown stripe fi-om the 

 orbit over the angle of the mouth. (From descr.) Hab. desert regions 

 about the Gila and Colorado rivers. 



The supraciliary is sometimes produced upward in specimens of C. cori- 

 fluentus, which see. 



