Royal Physical Society. 189 



had at first concluded that the former were all strictly dermal. 

 On carefully removing this bony investiture, however, plate 

 by plate from the head, it was found that several plates, which 

 in every other part of the body are dermal, had assumed the 

 character of permanent bones of the head at and around the 

 vertex. This is a condition which may probably exist in other 

 animals of the same type. In the alligator, and its allies, 

 something of a similar nature occurs, and in the saurians of 

 the coal age, there is what may be pronounced a strictly iden- 

 tical arrangement. 



In studying the skeleton of the serpent, one is constrained 

 to view it as essentially a vertebral column, of very admirable 

 workmanship and adaptation, surmounted by a head which, 

 small as it is comparatively, seems principally to be occupied 

 in giving place and development for the sentient organs, but 

 which, besides, in the venomous tribes, is a startling array of 

 delicate and appropriate machinery for supply and defence ; 

 in the innocuous serpents for the former purpose only, so ar- 

 ranged as to encompass what may be viewed as an enlarged 

 or elongated vertebra, the brain-pan proper, forming a small 

 portion of the head, namely, in the slow-worm, one-third in 

 length, or l-78th of that of the entire animal. 



In the Anguis fragilis the bones of the head are more com- 

 pact than those of serpents. It has a single row of teeth in 

 each jaw, widely apart, on a bony setting, and so placed that, 

 viewed from without, half the length of the basement portion 

 is concealed by an over-lapping part of the jawbone, the 

 pointed and curved portion only being seen above the edge of 

 the bone ; an arrangement closely analogous to that observed 

 in the bone-clad sauroids of the carboniferous epoch. 



The number of vertebrae in the whole length of the animal 

 is 132 ; but if advantage be taken of a peculiar subdivision 

 of the caudal portion, to be afterwards adverted to, the num- 

 ber will be considerably greater. The whole column may 

 be arranged into 2 vertebrae in the neck, 58 in the trunk, 1 

 in the lumbar region, 2 in the sacrum or pelvis, and 69 in the 

 tail. 



The cervical consist of the atlas and dentata, which are 

 very easily distinguished from each other, the atlas having 



r2. 



