INJs^OCUOUS SERPENTS. 
1:^9 
except in the head and the plates which cover it being less, 
and in the abdomen being a little angular. Beneath, yel- 
low, the upper parts of a smoke-grey, sometimes approach- 
ing to a greenish, sometimes to a bluish hue. S. 140 + 50. 
B. S. 19. 
I have arranged, as an appendix to the genus Xenodon, 
an Ophidian of uncertain origin, but which probably comes 
from Brazil : it is our 
8. Xenodon bicinctus. It approaches the Coronella, 
and has a pretty robust form. The eye is bordered by a 
circle of 6 plates, and the rostral is very depressed. The 
body is surrounded by broad bands or double rings of 
brown, disposed on a yellowish ground, and forming below 
square spots. S. 192 + 89. 
HETERODON. 
The snakes of this genus are Coronellse, or rather Xeno- 
dons, with the head prolonged into a conical muzzle, gene- 
rally terminated by a hard salient plate, truncated at the 
extremity. They have only been observed in the New^ 
World, where they inhabit sandy places. The other plates 
of the head are less than ordinarily developed. The pre- 
dominant colour is red, relieved by spots or rays of a dark 
colour. These animals do not attain a large size, and they 
are among the rarest of Ophidians. 
1. Heterodon Platyrhinus is the best known, and is 
distinguishable by its massive and vigorous form, and 
especially by its turned-up rostral plate, projecting in the 
form of a crescent ; it has several frontal scales, and the 
labial plates are very high. Scales lanceolate, carinated, 
and disposed in 21 rows. S. 124 + 38. Body cohered 
with wide, dark spots, on a reddish-grey ground. Coun- 
try, North America. Brazil produces a climatal variety 
of the same species. 
2. Heterodon Bhinostoma, a native of Brazil, re- 
sembles the last in the form of its rostral plate ; but this 
part is smaller in this species ; the plates on the head af- 
fect a more regular figure ; its scales are smooth, and dis- 
