CROTALUS LUCIFER. . 189 



The dorsal scales are disposed upon twenty-five longitudinal series, 

 narrowest on the back, tapering and rounded posteriorly, provided 

 with a strong keel. Towards the sides the scales slightly increase 

 in size, whilst their keel becomes obsolete till it almost entirely disap- 

 pears upon the external two series, which are, at the same time, the 

 broadest. The abdominal scutellae are rather narrow, about one hun- 

 dred and sixty-six in number. The preanal one is entire, as well as 

 the subcaudal scutellae, which number from twenty to twenty-five. 

 The rattle is composed of six rings and a half. 



The total length of the largest specimen described is twenty-seven 

 and three-fourths inches, of which three and three-fourths inches 

 belong to the tail. 



The ground color is light above. Along the back there is a series 

 of subhexagonal or octogonal blotches, formed by a skeleton of a dull 

 yellow, constituting a dorsal chain. The space of the ground color 

 thus inclosed is faintly margined with dark brown ; the width of the 

 interval between the successive blotches is from one half to one and a 

 half scales. These spots are frequently confluent, two and three run- 

 ning together. Where most distinct, the spots are four scales long and 

 eleven wide. On each side of this dorsal series is a second, separated 

 by a single row of scales ; the blotches extending from the abdominal 

 scutellae to the fifth or sixth row. These are smaller than the dorsal 

 and subcircular. Opposite the transverse light bands, and in the open 

 space between four contiguous blotches on the sides, smaller blotches 

 may be indistinctly observed. Posteriorly, the spots on the back 

 and sides are confluent and darker ; in one specimen forming seven- 

 teen half-rings, encircling the upper region, leaving about twenty-four 

 dorsal blotches. The abdomen is greenish-yellow, more or less clouded 

 with brown at the bases of the scales. The head is dark brown ; a 

 light line extends from the posterior portion of the supraoculars along 

 the fourth row of supralabial scales to the angle of the mouth. The 

 same light color is observed upon the upper labials, and whole front 

 and side, leaving only the top of the head dark. The space about the 

 facial pit is darker. 



The theory of coloration is that of decussating lines, which, when 

 they intersect, unite so as to have the angles of intersection truncated. 



The species has a general resemblance to G. atrox in the arrangement 

 of the blotches, but it is darker, and has about seventeen dark half-rings 

 posteriorly, instead of four or five. In C. atrox the head is narrower 



48 



