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 

 curv^e of its back, and consequently has the number of 

 ranges equal, which is more remarkable, as it is unique 

 in the wdiole order of Serpents. 



One is led to believe that the transverse ranges of scales 

 should always be equal to the number of the vertebra?, 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 wdth a great number of small square scales, such 

 as the Boa, Eryx, Sea- Snakes, &c. On examining the 

 scales of those serpents, w^e 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: w^e designate these scales, proper to the gi-eatest 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 



