122 VENOMS 
spots, longer than broad, and a series of transverse dark bars on 
each side ; belly vellowish, spotted with blackish-brown. 
Total length, 200 millimetres ; tail 22. 
Habitat: Vera Cruz, Mexico. 
(d) Crotalus (Rattle-Snakes). 
These snakes differ from all others in that the end of the tail 
bears a series of large conical scales, forming rattles, each fitting 
into the next and movable in such a manner that when the reptile 
causes them to move they produce a strident sound (fig. 72). 
OODLE 
a b c d e ip g h 
Fic. 72.—A, Horny appendage (rattle) of Crotalus 
horridus (three-quarters natural size. After Garman). 
B, longitudinal section of the same. C, separated 
segments of the appendage: a, terminal point; /h, 
basal segment (after Czermak). 
are of the size of a large almond. 
B 
The 
these animals often 
exceeds 2,000 mil- 
The head 
very large 
length of 
limetres. 
is fat, 
and expanded pos- 
teriorly, and ter- 
minated in front by 
a short, truncate 
snout; it 1s covered 
above with scales or 
small shields. 
Rattle - Snakes 
are armed with enor- 
mous fangs enclos- 
ing acompletecanal, 
which extends 
throughout almost 
their entire length. 
The poison - glands 
The number of segments in the rattle is variable, but rarely 
exceeds 18 or 20. 
At the time of the shedding of the skin these 
