Orbicular Lizards, or Horned Agamas. 383 
bases anterior, forming the outer border, which projects slightly be- 
yond the general border, and is bluntly serrated in the middle, and a 
with a dental process at the basal angles:—of the twelve plates 
composing the sternum, all are of different shape and size, the cen- 
tral longitudinal suture irregularly curved. 
Head of moderate size, rather depressed ; the upper jaw armed 
at its apex with two strong dental processes :—color of the crown 
of the same dark olive, mottled with black and yellow, as the rest 
of the animal—throat and neck with bright yellow longitudinal lines, 
which extend on the fore feet:—tbe inferior surfaces of the mar- 
ginal plates marked with black bands striped with yellow. 
Tail of the ordinary dimensions of animals of this genus ;—the 
same may be observed respecting the feet; the anterior nails are 
longer than the hind nails ; in both, the middle nails are the longest. 
Dimensions.—Length of the back plate 8 inches; breadth of the 
same 6 in.: length of the sternum 7 in. ; breadth of the same 4 in.: 
depth of the animal 2 in. 2 tenths: length of the head 23 in.; 
breadth of the same 1 in. 1 tenth: length of the longest claw 6 
tenths ; length of the longest posterior claw 4 tenths. 
General Remarks.—My friend Thomas Nuttall, whose indefati- 
gable exertions in natural history have extended throughout North 
America, on his recent travels across the continent to the Pacific 
Ocean, obtained the present specimen in the fresh water ponds in 
the vicinity of the Oregon or Columbia River, where this species 
was observed to abound, to the exclusion, according to his observa- 
tion, of any other tortoise. 
Arr. XXIII.—Notice of the Orpicunar Lizarps, or horned 
Agamas ; by R. Haruan, M. D., &c. 
Amone the valuable treasures in natural history, recently brought 
by Mr. Nuttall from his journey across the Rocky Mountains to the 
- Pacific Ocean, are several excellently preserved specimens of a large 
species of Orbicular lizard, which he kindly placed at my disposal 
for the purpose of description. Mr. Nuttall obtained his specimens 
in California, and preserved them living for many weeks: he con- 
sidered them of a very docile nature, never attempting to use their 
horns in self-defence ; they inhabit under stones, and in holes, in the 
