190 
OIT THE PHYSIOGNOMY OE SEEPENTS. 
rows of dark oval spots ; a broad black streak behind the 
eye. Japan. 
13. Trigonocephalus Cenchris. — From North Ame- 
rica. Very distinguishable by its small occipital plates 
(which are sometimes entirely wanting), and by the scales 
of the occiput, which are roughened into tubercles instead 
of keels ; form massive. S. 130 + 43. Body ornamented 
above with large bands of coppery brown, which permit 
the ground colour to appear as large lozenge-formed spots, 
of a greyish colour. 
CEO TALUS. 
The second genus of the True Venomous Serpents. They 
are peculiar to the New World, and prefer inhabiting dry 
uncultivated places ; we may say, that they take the place 
of the Vipers in both Americas. They have the nasal 
fosse like the Trigonocephalus ; but their form is more 
robust, their head thicker, their tail armed at its extre- 
mity either with a sounding instrument called a rattle^ or 
with a hard scale prolonged into a long and sharp point. We 
only know four species of this genus, some of which arrive 
at a size superior to any other venomous snake. 
1. Crotalus horridus. — The great Crotalus of South 
America. It has a muzzle covered with 3 or 4 pairs of 
plates ; 29 rows of lozenge-formed scales, surmounted with 
a sharp carina. S. 145 + 25. Above of a yellowish brown, 
variegated on the back by a range of broad lozenge-shaped 
spots. 
2. Crotalus Durissus. — Keplaces the last in North 
America, and is found in Mexico. Very much allied to 
the C. horridus ; but it has only 2 pairs of plates on its 
muzzle ; the carina on the scales is less developed, the eyes 
are smaller, the colours darker, the spots often form bands, 
and the tail is black. S. 170 + 22. 
3. Crotalus miliarius. — A small species of North 
America. Very recognisable by its head, covered on the 
top with 9 well developed plates ; 23 rows of scales. S. 
131 + 26. Eye large ; colour a reddish grey, varied by 
three series of darker spots. 
