G 



ENERA AND SPECIES OP THE RATTLESNAKES. 123 



"1801. Crotalus atricaudatus : Latreille, Hist. Rept., Ill, 209." 



Ig21. " " ?BoiE, Isis von Okcn, p. 562. 



J830. " " ?Wagler, Nat. Syst. Ampbib., p. 111. 



1842. " " Gray, Zool. Miscell., p. 51. 



1843 Urocrotalou clurissus : Fitzinger, Syst. Rept, p. 29. 



1849 Uropsoplius clurissus: Gray, Catal. Brit. Mus., p. 19. E.kcIus. cit. Linn, et homon. conflu- 

 cntus Say, rlwmhifer Latr., triseriatus Wiegm. Wagl. Gray. 



1826. ? Crotalus Catcsbaei Hempr.: Fitzinger, Neue Class, p. 63, fide Gray. 



185l" ?Urocrotalon Catesbyanum Fitz.: Diesing, Syst. Helminth., II, 431. 



Icones.-Catesby, Hist. Car., II, tab. xlii. LaccpMe, Serp., II, tab. xviii, f 3. Shaw Zoo . 

 Ill t lxx.xviii. Daudin, Y, t. Ixviii. Guerin, Iconogr. R. Animal, t. xxm, f. 2. Selilegel, 

 Ess'ai XX f 15 16. Diet. Univ. Hist. Nat. Atlas, II, t. xiii. f. 1. Dura. Bibr. Erp. Gen. 

 Atlas, t. Ixxxiv, bis. fig. 1. Holbrook, N. Am. Herp., Ill, t. i. De Kay, Zool. New York, 

 pt. Ill, Atlas, fig. 19. Baird, Serp. New York, t. i, f. 1. U. S. Pac. R. R. Expl. Rep. 

 X, Reptiles, t. xxiv, fig. 1. 

 Habitat.— In "United States" orientalibus, usque ad "The Plains." 



This species may be distinguished by the following peculiarities :— 

 U.wn the top of the extremity of the muzzle there are two subtriangular shields 

 ' (prefrontals) in contact with each other. ' A large oval shield covers the region 

 over each eye (superciliary). These shields are in contact anteriorly upon each 

 side with a smaller one, which is in contact anteriorly with the prefrontal, and 

 forms upon each side, the external shield of a cross series (post-frontals) imme- 

 diately behind the prefrontals, which is usually composed of five plates. The 

 remaining part of the upper surface of the head is covered with small subtuber- 



culous scales. , , r i. 



The shields bounding the upper lip (superior labials) are from twelve to fourteen 

 in number, the fourth or fifth the largest; those bounding the lower lip inferior 

 labials) thirteen to fifteen. Three rows of scales separate the eye from the supe- 

 rior labials. Two plates in front of the eye (preoculars), the lower usually reach- 

 in- the pit in the side of the face; the upper larger, and separated from the 

 hinder of the two plates between which the nostril is pierced (nasals), by two or 

 more small plates (loreals). The scales of the body are in twenty-three or twenty- 

 five longitudinal rows, all keeled, the row on each side next the shields of the ab- 

 domen (gastrostega) faintly. x 1 1 ,• 



The ground color above varies from bright yellowish tawny or fulvous to black 

 brown ; beneath from whitish yellow to black gray. A light line extends from the 

 superciliary plate to the angle of the mouth, behind which is a dark band or blotch. 

 Upon each side of the medial dorsal line there are two series of brown or black 

 spots The spots of the upper or medial series are larger, rhomboid, running 

 obliquely upwards and baclcwards. They are frequently confluent across the 

 middle line of the back anteriorly; ahoai/s upon the posterior half of the body. 

 The spots of the lower series encroach slightly upon the gastrostega, and poste- 

 riorly, unite with those of the middle series, to form zigzag cross bands. Ante- 

 riorly they sometimes alternate with the central series, or rather become confluent 

 with an indefinite alternating series, and joining the extremities of the former, 

 enclose the ground color, which thus forms a series of light spots. Of these trans- 

 verse bands or rows of spots there are twenty-one, more or less, from the head to 



