OF THE INTEGUMENTS. 
71 
anomalies are frequently observed in different individuals 
of the same species, and this number is even far from being 
the same in different regions of the body : it is on the 
neck, at a short distance from the head, that the ranges of 
the scales are most numerous. Towards the middle of 
the trunk they begin to diminish, the two scales next the 
abdomen being replaced by one : these ranges disap- 
pear one after another, and at the end of the tail they 
are reduced to a single scaly plate. The number of longi- 
tudinal ranges is almost always unequal ; Ophidians 
having the middle line of the back furnished with a single 
row of scales, sometimes larger and of a different form 
from the rest. The only exception to this is the Herpeto- 
dryas carinatus, which has two ranges of scales along the 
curve of its back, and consequently has the number of 
ranges equal, which is more remarkable, as it is unique 
in the whole order of Serpents. 
One is led to believe that the transverse ranges of scales 
should always be equal to the number of the vertebrae, or 
to that of the plates which defend the lower part of the 
trunk ; but it is not so in the Ophidians whose bodies are 
invested with a great number of small square scales, such 
as the Boa, Eryx, Sea-Snakes, &c. On examining the 
scales of those serpents, we find, on proceeding from the 
abdomen, that the ranges of the scales, at first broad, be- 
come narrow, and lose themselves among other ranges of 
very small scales that descend from the back. 
The modifications of form which the scales present in 
the different species of serpents, are infinitely varied. Their 
edges are sometimes rounded, sometimes truncated at the 
end, at other times pointed more or less acutely. Their 
epidermis is generally very hard, and the edges of the scales 
salient, so that they cover each other like the tiles of a 
roof : we designate these scales, proper to the greatest num- 
ber of Ophidians, imbricated. Other Ophidians, on the 
contrary, especially sea-serpents, with the exception of a 
single species, have their scales covered with a very thin 
epidermis, and these organs, usually very small, present an 
hexagonal form. The skin in the intervals of the scales 
in these Ophidians, is much less dilatable than in other 
