PLATANISTA. 545 



notch from an inferior process, wliich, however, is continuous at its base with the 

 foramen. In an older animal, the vertebra is ossified, but the neurocentral suture 

 cuts through the notch which separates the superior from the inferior process, and 

 the latter is seen to be an autogenous element developed at the inferior external angle 

 of the centrum below the neurocentral suture, while the superior transverse 

 process, as in the preceding vertebrae, is an exogenous product of the neural 

 arch. 



In the fifth and sixth vertebrae, a similar condition of things exists, only the 

 inferior autogenous process becomes more strongly developed as it is traced to the 

 sixth, where it occupies the same position as in the fourth vertebra. 



In the seventh vertebrae of the foetus, there is a cartilaginous interval between the 

 neural laminae ; the transverse process is unossified, the pedicles are separated by a 

 cartilaginous interspace from the centrum, and the position of the inferior transverse 

 process on the side of the centrum in the previous vertebrae is occupied by the 

 facet for the head of the rib. In the more mature skeleton before me, the neural 

 laminae have nearly united ; the superior transverse process is fully ossified ; and the 

 neurocentral suture is at a higher level than in the preceding vertebrae and has a 

 more outward course. A portion of the head of the first rib has been brought away 

 in separating the vertebra from the first dorsal, and is attached to the outer 

 extremity of the neurocentral suture, between the external margin of the base of 

 the pedicle and the lateral surface of the centrum, being chiefly applied to 

 the latter and simulating the inferior transverse process of the sixth cervical 

 vertebra. 



There is this remarkable fact also connected with this same animal that the 

 superior transverse process of each side bears at its extremity what must be 

 regarded as the rudiment of the tubercular portion of a cervical rib, much more 

 intensely developed on the right than on the left side. This condition of things is 

 the very opposite of that which prevails in the last dorsal vertebra, in which the rib 

 is borne on the extremity of the autogenous transverse process of the centrum of 

 the tenth dorsal ; which process is serially homologous with the autogenous transverse 

 process of the lumbar region and with the similarly originated processes of the 

 (cervical vertebrae. It may be regarded as an enormously developed epiphysis of 

 the superior transverse process simulating the portion of the rib distal to the 

 tubercle; but it must be kept in mind that no other of the epiphyses of the 

 vertebral process are developed. 



The neurocentral suture in all the cervical vertebrae is intact, but in a still 

 older skeleton the suture only exists in the seventh vertebra, having disappeared in 

 all the others, and the inferior transverse processes are completely united with their 

 respective centra. 



In the dorsal region, the tubercles become more and more approximated to the 

 heads of the ribs as they are traced backwards, till at last in the sixth, but more per- 

 fectly in the eighth, rib they are merged in one articular surface, which is exclusively 

 applied to the transverse process of that vertebra which occurs on the side of the 



w 3 



