VERTEBRA OF THE RATTLESNAKE. 85 



■H 



broader than they are long ; there are no superorbitals. 

 A strong ridge is developed from the under surface of 

 the basisphenoid, and a long and strong recurved hypa- 

 pophysis from that of the basioccipital ; these give inser- 

 tion to the powerful " longi-colli" muscles, by which the 

 downward stroke of the head is performed in the inflic- 

 tion of the wound by the poison-fangs. 



The characteristics of the trunk- vertebra of the ophi- 

 dian reptiles are as follows : The autogenous elements, 

 except the pleurapophyses (Fig. 16), ^j?, coalesce with 

 one another in the vertebra of the trunk ; and the pleu- 

 rapophyses also become anchylosed to the diapophyses 

 in those of the tail. There is no trace of suture between 

 the neural arch (26.), ??, and centrum, c. The outer sub- 

 stance of the vertebra is compact, with a smooth or 

 polished surface. The vertebrae are 

 " procoelian ;" that is, they are articu- 

 lated together by ball-and-socket joints, 

 the socket being on the fore part of the 

 centrum, where it forms a deep cup 

 with its rim sharply defined ; the cavity 

 looking not directly forwards, but a 

 little downwards, from the greater pro- ^ 



minence of the upper border; the well- vertebra of the 



, ^ . . 1 n i • - x1 RATTLESNAKE ((7>ofa- 



turned prominent ball terminates the ^. 

 back part of the centrum rather more 

 obliquely, its aspect being backwards and upwards. 

 The hypapophysis, hy^ is developed in different propor- 

 tions from different vertebras, but throughout the greater 

 part of the trunk presents a considerable size in the 

 cobra and crotalus (Figs. 13 and 16), hy; it is shorter in 

 the python -and boa. A vascular canal perforates the 

 under surface of the centrum, and there are sometimes 

 8 



