HOLLAND AND PETERSON: OSTEOLOGY OF THE CHALICOTHEROIDEA. 267 
Vertical height of posterior end of centrum measured perpendicularly.......................-.. 55 
Greatest height of keel of centrum below transverse processes... . 1.2.0.0... eee eee ee eee eee 27 
Distance to neural canal from bottom of keel of centrum at middle.................-.....000-. 45 
siransyerse diameter okmneunralecpineimeirOnte ene meeeriea eerie aa nani race acre pie talk 
Transverse diameter of neural spine above origin of postzygapophyses.............-.+--..-+0-- 27 
ANITELO=POSteHOMCdlAamMEeterEOtaspinerallOlieine sa eei relate reais oi tei oe ee iia 42 
Antero-posterior diameter of spine at upper extremity. .............0 000 e cee eee ee eee 35 
HCIShE Ores pINeE rom Ori Cierny eee rent acre vie een por aU ea eiey saniclisom cere toners eee elev ala sal vacel ay at «levies 60 
Antero-posterior diameter of outer margin of transverse process... ............0 eee ee eee tees 70 
TrAMsvOrRe Glinimneier OF POrcorminiGmall CAM, odo0cccesvg900de00dcnnba0cDDvGGvoUEDduRUGOD CEOS 10 
20 
Supero-inferior diameter of vertebrarterial canal 
The Sixth Cervical Vertebra.. 
On comparing the sixth cervical with the fifth we detect a profound modi- 
fication of the lower surface of the centrum and the transverse processes in the 
former, which also becomes much shorter in some of its antero-posterior dimensions. 
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Fig. 38. Ventral view of sixth cervical of M. elatus 
Fic. 37. Lateral view of sixth cervical 
(No. 1604). X#. 
of M. elatus (No. 1604), X43. 
The long thin keel of the centrum, which is so characteristic a feature of cervicals 
2-5 is very greatly reduced in the sixth and becomes a low broad ridge not more 
than five millimeters in height. The posterior part of the inferior lamina of the 
transverse process which in the preceding vertebrae is shown to carry upon its 
superior surface a fossa in continuation of the vertebrarterial canal widens out 
laterally and downwardly and fuses with the main body of the transverse process 
in front in such a way as to wholly obliterate the horizontal posterior marginal 
