HATCHER : DIPLODOCUS (mARSH) 21 



The neural spines and transverse processes especially are not well preserved. 

 Fortunately the centra, neural arches and zygapophyses are for the most part com- 

 plete. These show that commencing with the third, the anterior zygapophyses are 

 prolonged anteriorly beyond the ball of the centrum. There are also in each of these 

 vertebrae, prediapophysial cavities. Owing to their imperfect condition in the region 

 of the cervical ribs it is impossible to determine the nature of those elements in the 

 vertebrae under consideration. In restoring these vertebrae the cervical ribs have 

 been ignored and the vertebrae restored as if they were wanting in each instance. 

 They were undoubtedly present, but it is impossible to determine whether the 

 transverse and capitular processes were in contact and enclosed a lateral canal and 

 whether or not there was an anterior branch of the cervical rib. The walls of the 

 pleuro-central cavities become successively less regular in these vertebrae, and while 

 consisting in C. 3 of a more or less flat and level floor of bone, in C. 4 and 5 the 

 floors are invaded by several vacuities which open into intramural cavities enclosed 

 within the outer walls of the centra. Commencing with C. 3 the neural spines of 

 these vertebrae have been restored as bifid both anteriorly and posteriorly, each 

 spine consisting of a broad thin plate of bone formed by the union of the pre- and 

 postzygapophysial laminae of their respective sides. These are made to appear free 

 anteriorly and posteriorly, but united, except at their apices, throughout the inner 

 sides ; conditions which prevail in the succeeding cervicals. 



Cervicals Six, Seven, Eight, Mne and Ten. — These vertebrae difler so little in their 

 more important characters that they may be very conveniently described together. 

 They are all fairly well preserved and show certain characters which are gradually 

 more emphasized in the succeeding vertebrae of the series. Commencing with C. 6 

 they regularly increase in length posteriorly. The neural spines become more com- 

 pletely bifid, resulting in a pair of transversely placed perfectly free spines on the 

 tenth cervical consisting of triangular plates of bone diverging superiorly and ter- 

 minating at the summit in a rather blunt, rounded process. The walls of the centra 

 in the pleurocentral cavities are successively interrupted by an increased number of 

 vacuities and these cavities are more or less completely divided into anterior and 

 posterior portions by strong bony plates (the pleuro-central laminae), running from 

 the base of the prezygapophyses obliquely downward and backward to the inferior 

 border of each centrum. These are especially noticeable in cervicals nine and ten. 

 Posteriorly the zygapophyses rapidly increase in size and the articular surfaces are 

 successively more expanded, in order to gives a greater area to those surfaces of im- 

 pact which were to resist the strains brought to bear upon them by the necessary 

 movements of the neck and head during the life of the individual. As we proceed 



