2536 



SCALED REPTILES 



glass covers the face of a watch. When a snake changes its skin, which it does 

 several times during the year, the discs over the eyes peel off with the rest, and ap- 

 pear as lenses in the dry slough. Equally characteristic is the absence of any 

 external aperture of the ear, a peculiarity which has given rise to the scriptural ex- 

 pression of the deaf adder stopping its ears. Resembling that of lizards in its 

 flattened form, the tongue of snakes is narrow and smooth, and terminates in a fork 

 formed by two long thread-like points, while at its base it is inserted into a sheath 

 from which it can be protruded at will. The head, although not very large, is gen- 

 erally wider than the body, from which, as already said, it is but seldom separated 

 by a recognizable neck, and is usually oval or triangular in shape, with a more or 

 less well-marked depression. Near the sides of its extremity, and sometimes at the 

 very tip, are situated the nostrils; while posteriorly the gape in some cases extends 

 almost to the back of the head. Superiorly, as well as on its under surface, the head 

 is generally covered with a number of large symmetrical shields, having their edges 



INFERIOR, LATERAL, AND SUPERIOR VIEWS OF THE HEAD OF A SNAKE. 



r. rostral shield;./?: anterior and posterior frontal do.; v. interparietal do.; s. supraocular do.; o. parietal do.; 

 nn 1 . nasal do.; 1. loreal do.; a. preocular do.; p. postocular do.; uu. upper labial do.; tf. temporal do.; m. mental do.; 

 ** lower labial do.; cc. chin shields. After Giinther. 



in apposition, and varying in relative size in the different groups. Although the 

 blind snakes have a uniform cuirass of polished scales all around the body, while 

 some of the sea snakes also have the scales of the under parts similar to those of the 

 back, in the great majority of the order the under surface of the body is protected 

 by large transverse shields, extending completely across it from side to side. These 

 broad shields often extend as far backward as the termination of the body proper; 

 while at the commencement of the tail, and thence backward to the extremity, they 

 are replaced by a double row. These large inferior shields take an important part 

 in the progression of snakes on land, and hence we see why they are wanting in the 

 marine forms. 



In all snakes the number of joints in the backbone is very large; and each of 

 these, with the exception of a few near the extremity of the tail, is provided with a 

 pair of rather long, slender, and curved ribs, the extremities of which correspond to 

 the large inferior shields of the body in the species where these are present. Supe- 



