CERVICAL VERTEBRAE OF CHELONIANS 215 



Before examining some turtle skeletons at hand, it may be 

 as well to quote the opinions of more recent authorities on che- 

 lonian osteology; we turn to the work of one of the best-known 

 writers on this subject of chelonian osteology — Doctor Hay, who 

 states ('02, p. 4) that "We may now examine the vertebrae in 

 front of and behind the dorsals. In all of the turtles there are 

 normally 18 presacral vertebrae, of which 8 belong to the neck. 

 The more anterior and the more posterior cervicals are shorter. 

 The neck as a whole is about as long as the dorsal series of verte- 

 brae. The first is composite, consisting of four distinct pieces. 

 On each side is a neural arch, aiding in forming the neural canal. 

 Below, these abut on a median piece, the hypocentrum. These 

 three bones unite in forming a concavity, into which fits the 

 ball-like occipital condyle. Behind the arches and the hypo- 

 centrum is the odontoid process, the proper centrum of the first 

 cervical. Behind, this articulates with the centrum of the 

 second cervical, but^ioesliot become anchylosed with it." 



Boulenger says ('89, p. 15) : "The cervical vertebrae, which 

 number eight as in all Chelonia, present this peculiarity that 

 their centra exhibit the four modes of articulation, some being 

 concavo-convex, others convexo-concave, others biconvex, others 

 biconcave. A single exception is known, Pyxis, in which they 

 are all procoelus in the specimen examined by Vaillant, as well 

 as in the one in the British Museum." Boulenger appears to 

 have examined the vertebral column of a number of the soft- 

 shelled turtles, but on the whole somewhat superficially. 



Indeed, it would appear that all of the recent writers on the 

 subject state that the chelonians have eight cervical vertebrae 

 in their spinal columns. As a final authority we may cite 

 Reynolds, who, in describing the cervical vertebrae of a turtle, 

 says ('97, p. 219) : "These are eight in number, and are chiefly 

 remarkable for the variety of articulating surfaces which their 

 centra present, and for their mobility upon one another." 



A number of our text-books on zoology, now in use in schools 

 and colleges, state that all chelonians possess eight cervical 

 vertebrae, but it would appear that the authors of such volumes 

 have never personally verified this statement, rather obtaining 

 it from the standard works on the subject of an earher date. 



joubnaij of morphology, vol. 35, no. 1 



