220 FOSSIL REPTILES. 



the larynx reposes, composed only of a cricoid cartilage, and two 

 annular arytenoids, so that the plate performs at one and the 

 same time the function of epiglottis, corpus hyoidis, and thyroid. 



The number of vertebrae is subject to some variation, but M. 

 Cuvier considers the average number to be sixty. In the young 

 the number is generally more complete, as their tail has not 

 been mutilated by any accident. He reckons in some seven 

 cervical, twelve dorsal, five lumbar, two sacral, and four-and- 

 thirty caudal. All these vertebrae, including the axis, have the 

 posterior face of their body convex, and the anterior concave. 

 An important remark, as will be seen hereafter. Both of these 

 faces are circular. In some young individuals, forty, and even 

 forty-two caudal vertebrae have been found. The last M. 

 Cuvier regards as the normal number, for the tail. 



The atlas is composed of six pieces, which, as it would ap- 

 pear, remain distinct during life, and are retained only by car- 

 tilages. The axis has five. With respect to the rest it would 

 be tedious to enter into details, and unimportant, at present. 

 Any variations that may occur in the fossil specimens shall be 

 duly noticed and explained. 



The ribs are twelve in number on each side, without reckon- 

 ing the appendages of the cervical vertebrae, which might very 

 well be named false ribs. The first, and sometimes the first 

 two ribs, have no cartilage to unite them to the sternum. The 

 following eight or nine have each a cartilage or sternal part, 

 which quickly ossifies, but which unites to the vertebral part by 

 an intermediate portion, which for along time, perhaps always, 

 remains cartilaginous. 



The sternum, even in the oldest individuals, has but one 

 piece, which is osseous. This is flat, elongated, pointed in 

 front and behind, the anterior part of which goes under the 

 neck in front of the coracoid bones, and the posterior part is 

 enchased in a cartilaginous, rhomboidal, or elliptical disk, at the 

 anterior lateral side of which is a groove into which the coracoid 

 bones are articulated. 



