124 ESCHRICHT AND REINHARDT 



and the spinous process and the arch from the eighth vertebra. Of chevron bones we have, in 

 the twenty-two feet long skeleton, as well as in the newborn specimen and the foetus, found the 

 jast traces between the thirteenth and fourteenth caudal vertebrae, so that fourteen of these are 

 altogether to be found in the species, they being only wanting between the eight posterior 

 vertebrae. 



While the bodies of the vertebrae gradually dwindle into smaller dimension from before 

 backwards, their shape is also, in the six foremost caudal vertebrae, modified by their having, on 

 their inferior surfaces, the anterior and posterior of the above-mentioned angles, not only 

 approaching each other like hooks, but, from the fourth vertebra to the seventh, meeting each 

 other, and arching over a canal on each side for the ascending lateral branches of the aorta. 



The alterations which the transverse processes are subjected to, as they dwindle away, are 

 also very well marked. In the first caudal vertebra they point very much in a forward direction, 

 and have their anterior margins excavated near to their roots, so that a groove is formed for the 

 lateral branch of the aorta. But already in the second caudal vertebra the foremost part of the 

 transverse process will be found to overbridge this excavation, changing it into a foramen. The 

 lateral branch of the aorta, while it ascends along the side of the vertebral body, runs first 

 along the groove formed by the two inferior lateral angles, and then through the canal in the 

 root of the transverse process. 



In the fourth caudal vertebra, where the lateral grooves in the inferior surfaces of the body 

 have already become changed into closed canals, the transverse processes have shrunk so much 

 that it is only quite anteriorly that they are seen projecting, looking like a pair of low 

 longitudinal ridges, dividing the two lateral surfaces of the body into a superior and au 

 inferior half; but they have, at the same time, been so much expanded at their roots upwards 

 and downwards, that the lateral surfaces are half covered by them, superiorly as well as inferiorly. 

 The lateral branch of the aorta has here only a short space, comparatively speaking, to traverse in 

 its way from the groove on the lateral edge of the inferior surface to the foramen in the transverse 

 process ; and, besides, this inferior part of the lateral surface has now become so much excavated 

 from beneath in an upward direction, that it looks itself like an open groove. The superior half 

 of the lateral surface has also at the same time become so much excavated, and in such a direction 

 as to leave distinct traces of the further course of the arterial branch after it has issued from the 

 hole in the transverse process, that is to say, behind the articular process and into the cavity of the 

 spinal cord. In the fifth caudal vertebra a hole through which the arterial branch is conducted 

 into the cavity of the spinal cord has also formed itself posteriorly in the articular processes. In 

 the sixth caudal vertebra, that open but deep groove on the inferior lateral surface appears still, 

 but only as a round hole leading into a canal having an upward direction in the interior of the 

 bone ; the transverse process is scarcely more than rudimentary, forming only a very indistinct 

 boundary between the superior and inferior lateral surfaces of the body. The bridge behind the 

 articular processes has also, in conformity with the root of the transverse process, been so much 

 expanded in breadth, that the part of the superior lateral surface not yet covered by these 

 articular processes, looks like a deep hollow with an outlet beneath leacUng to the canal, and 

 another above leading into the cavity of the spinal cord. In the sixth caudal vertebra the cavity 

 of the spinal cord is so much constricted as scarcely to measure one inch in diameter, the spinous 

 process is now only very slightly prominent, and the articular processes are changed into a pair 



