1856.] 249 



the largest; immediately behind the middle post-ocular one temporal plate be- 

 tween the occipital and the superior labials ; 23 rows of carinated scales, the 

 inferior row but slightly carinated and larger than the others ; scales strongly 

 emarginate posteriorly, the carinae running the whole length of the scale ; scales 

 long and ratber narrow upon the back, broader towards the abdomen. 140 ab. sc. 

 1 bifid pra3anal, and 69 sub caudal ; tail rather long, tapering to a point ; body 

 robust, size about that of Tr. sipedon. 



Coloration. Greyish above, with large transverse and more or less oblique 

 blotches of the same color bordered with black, extending as far as the abdo- 

 minal scales; they are quite broad, occupying about five rows of scales, and have 

 very irregular margins ; the interspaces between them are comparatively very 

 narrow, from a scale to nearly two in width ; 32 of these oblique blotches may 

 be counted, the 32d opposite the anus ; 18 or 19 transverse brownish bands 

 upon the tail; under surface resembling very much that of sipedon, the ground 

 color yellow, which predominates greatly at the anterior part; throat and under 

 jaws quite yellow, the posterior margins of the inferior labials bordered with 

 brown. 



Dimensions. Length of head 1 inch 5 lines ; greatest breadth 9 ; length of 

 body 2 feet, 1 inch, 7 lines ; of tail 8 inches; total length, 2 feet, 10 inches, 1 

 line ; circumference 3 inches, 1 line. 



Gen. Remarks. This serpent differs from Trop. rhombifer and transversus. 

 It resembles very much a specimen in the possession of Dr. Holbrook from 

 Chicago, sent to him sometime ago by Prof. Kirtland, and which he has kindly 

 permitted me to examine. They both are of the same length, have similar mark- 

 ings, and the same number of rows of scales. It may be a variety of Trop. 

 sipedon. 



Heterodon nasious. 



There are three specimens of Heterodon nasicus B. and G., in very excellent 

 pieservation. These Heterodons are remarkable for their prominent rostral 

 plate and bulging cheeks, giving them a physiognomy, to use the expression of 

 Prof. Scblegel, quite different from that of our ordinary Heterodons. The abdo- 

 men and under part of tail is almost entirely black. In two of the specimens the 

 vertical (frontal) plate is as broad as long, in one broader by about half a line ; 

 the shape of the vertical plate differs entirely from that of simus, but much more 

 from that of niger and platyrhynos. In a specimen of simus there are eight 

 small plates between the frontal and rostral, and the anterior nasal and su- 

 pero-nasals; in nasicus 'fourteen, in platyrhynos and niger there is but one, 

 (the azygos) immediately behind the rostral. In a specimen of niger there is 

 but one loral plate, the posterior supra-nasal (posterior frontal) passing down 

 upon the side to take the place of the upper one in simus ; and in platyrhynos 

 two. The entire length of the largest of these specimens of nasicus is one 

 foot, three inches, tail 2 inches 7 lines, circumference 1 inch 7 lines. It appears 

 to be a smaller species than simus, and much smaller than platyrhynos and 

 niger. Prof. Baird and Girard, however, give over two feet as the dimensions 

 of a specimen from Sonora. Ab. sc. 137, 1 bifid praeanal, 43 sub-caudal. In 2d. 

 137, ab. sc. sub-caud. 43. In 3d, 137, ab. sc. sub-caud. 44. 



Habitat. Rio Grande, Red River, Arkansas, Fort Webster, Sonora. 



Gen. rcmarlcs The figure in Capt. Marcy's report does not accurately repre- 

 sent this animal ; the bulging of the cheeks, a prominent characteristic, is not 

 sufiSciently shown, and the nostril is in a single plate, which is not the case. 



VENENOSI. 



Trigonocephalus contortrix. 



There are four specimens of Trigonocephalus contortrix, which present no- 

 thing very peculiar. In one of them the black color predominates greatly upon the 

 abdomen; dorsal rows of scales near the middle in all 23. In a fine specimen 

 from Pottsville, Pa., presented by Mr. C. T. Hughes, the dorsal rows are but 21, 



