1852.) 127 
lar, very thin, without carinz and finely denticulated posteriorly. On the sides, 
the upper part of the legs and on the tail, the scales taper posteriorly into a sharp 
point. The plates on the upper surface of the head are rather small and irregu- 
lar in shape, except the occipital, which is larger than in any other allied species. 
The general color is olivaceous, reddish on the back and sides, with transverse 
dorsal black bands, much broader and more distinct on the tail. There is alsoa 
black collar convex backwards, embracing the region of the neck above and 
terminating in advance of the origin of the fore legs. 
At the request of Col: J. D. Graham, we have dedicated this species to the 
memory of the late Hon. Joel R. Poinsett, whose name is associated with the 
progress of science and the useful arts throughout his public career, especially 
while Secretary of War of the United States. 
Localities.—Rio San Pedro of the Rio Grande del Norte, and the province of 
Sonora. 
SceLoporus Crarxi, B. and G.—Allied to both Se. torguatus and Sc. spinosus, 
it resembles the former in the presence of an imperfect black collar, which is 
more distinct in the young. ‘This, however, is never seen to forma complete 
crescent on the neck, but is gradually diminishing in width from its origin in 
advance of the fore legs towards the upper part of the body. From Se. spinosus 
it differs by-having proportionally much larger scales on the temporal region, and 
all the scales terminated by a much less developed posterior point. The body is 
uniform yellowish green, excepting the band of black on the sides of the head. 
The male has a bluish abdomen, indistinctly black along the middle region. The 
lower surface of the head is blue, on the middle region surrounded with black. 
Dedicated to John H. Clark, to whose skill as a collector, and untiring zeal for 
science, the world is indebted for the splendid zoological collections sent and 
brought home by Col. Graham from the survey of the Mexican boundary. 
Locality.—Province of Sonora. 
Scenororus THayeri, B. and G.—This species has the general appearance of 
Sc. scalaris and Se. gractosus. It differs from both by a very readily apprecia- 
ble character, which consists in the possession of much larger scales on the upper 
region of the body. The color is yellowish green above, with two longitudinal 
bands of brown or black, and two yellow ones, on each side. Sometimes, instead 
ot bands, a series of small patches of the same color is observed, the black 
patches also form transverse and undulating narrow bands. The belly is uniform 
yellow underneath, the male has on each side an elongated patch of blue, witha 
narrow band of black along the abdominal margin. Under the throat there is a 
medial black patch, limiting on each side another blue spot. 
At the request of Col. Graham likewise, we have dedicated this species to Col. 
Sylvanus Thayer, of the U.S. Engineer corps, and the founder of the present 
system of instruction at the U. S. Military Academy at West Point, as a tribute 
to the high scientific attainments and valuable services in his profession as an 
officer. 
Localities.—Indianola, on the Gulf of Mexico, San Antonio, (Texas,) El Paso 
del Norte, and as far westward as the province of Sonora. 
ScELoporus pispaR, B. and G.—No species of the genus Sceloporus will be 
more easily recognizable than the present one, on account of the great disparity 
which exists between the scales on the upper part of the body and those on the 
tail, the latter being twice as large and more strongly carinated. The scales on 
the abdomen are likewise a little larger than those on the back. The color in the 
only specimen which we have hitherto seen of this species is uniform blackish 
green, but as it has been collected for a long time, the color may have changed 
considerably. The head is reddish brown. The abdomen in the male is blue 
from the fore to the hind legs, leaving a medial narrow space of the color of the 
throat and thighs, and along whicha narrow black band separates it from the 
blue. 
Locality.—Vera Cruz. Sent by Dr. Burroughs to the Academy of Natural 
Sciences of Philadelphia, where the specimen described is preserved. 
