REPTILES. 27$ 



TI. Body destitute of feet. 



OPHIDIA. 



In this division of Reptiles, which includes the Ser- 

 pents, the skin consists chiefly of a cuticle and co- 

 rium. The cuticle exhibits considerable differences in 

 thickness, and, as happens to the lizards, is periodically 

 cast off and renewed. The corium is destitute of a villous 

 surface, and intimately connected with the muscular web 

 underneath. The appendices of the skin consist exclu- 

 sively of scales. These are divided by naturalists into two 

 kinds. The true scales or squama, are usually produced 

 longitudinally, and pointed or rounded posteriorly. They 

 have, in general, some asperities on the surface. The 

 shields or scicta are of much larger dimensions, and pro- 

 duced transversely. In some cases they embrace the whole 

 of the body, forming rings ; in other cases, a half or a quar- 

 ter of one side only. They usually present a smooth sur- 

 face, and occur chiefly on the belly, between the throat 

 and vent. They difrer considerably in number in different 

 species, and even in. individuals of the same genus, so that 

 the character furnished by their number should be employed 

 with caution in the discrimination of species. There does 

 not appear to be any well marked secretion from the skin, 

 nor are there glands from which it could proceed. Between 

 the nose and the eye, indeed, on each side, there is a bag 

 or crumen in some species, not unlike the bags which oc- 

 cupy the same position in some of the ruminating animals. 

 Here, however, there is no appearance of glandular struc- 

 ture yet discovered, and the cuticle with which they are 

 lined, appears continuous, and falls off along with that 

 wliich covers the rest of the body. Dr TvsoN first ob- 

 served these crumcns in the rattlesnake, and Dr Russell 



