CROTALUS. 9 



blotches. Anteriorly the interval between the dark spots is but a 

 single scale; posteriorly it is more, becoming sometimes two scales, 

 where also the spots are more rhomboidal or lozenge-shaped; nearer 

 the tail, however, they become transversely quadrate. The funda- 

 mental theory of coloration might be likened to that of Crotalus 

 adamanteus, viz, of forty or fifty light lines decussating each other 

 from opposite sides; but the angles of decussation, instead of being 

 acute, are obtuse, and truncated or rounded off throughout. Along 

 the third, fourth, and fifth lateral rows of scales is a series of indis- 

 tinct brown blotches covering a space of about four scales and falling 

 opposite to the dorsal blotches: between these blotches, and opposite 

 to the intervals of the dorsal blotches, are others less distinct. 

 Along the fifth, sixth, seventh, and eighth rows is a second series- of 

 obsolete blotches, each covering a space of about four scales, and just 

 opposite the intervals between the dorsal spots. The dorsal and 

 lower series are separated by an interval of three scales, this interval 

 light brown. Beneath, the color is dull yellowish, and ten or twelve 

 darker half rings are visible on the tail. 



In point of coloration the principal features, as compared with C. 

 atrox, lie in the dorsal blotches, being disposed in subquadrate spots 

 instead of subrhomboids ; the intervals thus forming bands across the 

 back perpendicular to the longitudinal axis. This tendency to 

 assume the subquadrangular pattern has broken up the chain-work 

 into isolated portions, as in Coluber eximius or Crotalojyliorus Urge- 

 minus. The intervals of the dorsal blotches are wide and darker in 

 the middle, while in C. atrox they are narrow, not linear, and uni- 

 color. The sides of the head present the usual light stripe from the 

 posterior extremity of the superciliary ; it passes, however, to the 

 angle of the jaw on the neck, along the second row of scales above 

 the labials. A second stripe passes in front of the eye to the 

 labials, widening there. A small light vertical bar is seen below the 

 pit, and another on the outer edge of the rostral. On the supercili- 

 aries are seen two light transverse lines enclosing a space nearly one- 

 third of the whole surface. In C. atrox there is a single median 

 line. Sometimes, as in C. atrox, the single blotches on the nape are 

 replaced by two elongated ones parallel to each other. 

 Red River. 180. 27. 29. 34. 4. Capt. Marcy. 



San Pedro, Texas. 181.28.27. Col. J. D. Graham. 



Bet. San Antonio)^ 188.23.27. 27.3. 

 and Jill raso. ) 



