36 PROCEEDINGS OF THE NATIONAL MUSEUM vor„ 69 



obliquely downward and backward. The posterior articular facets 

 (pi. 12, ti<j^. 4) for the axis are subovoidal with convexo-concave sur- 

 faces and are set off from the posterior face of the centrum by dis- 

 tinct margins. The hyapophysial process is short, thick, and emargi- 

 nate. On the upper surface of the hyapophysial process and at the 

 base of the pyriform neural canal there is a large heart-shaped facet 

 for articulation with the odontoid process of the axis. 



Axis. — In comparison to the axis of Delphinodon dividum, this 

 vertebra is considerably smaller, measuring 57.7 mm. in height and 

 62.5 mm. between the extremities of the inferior transverse processes, 

 and its greatest thickness anteroposteriorly is more than one-fourth 

 of its breadth, or 16.7 mm. The neural spine is stout, thick at the 

 base, and is inclined backward; the posterior face of the spine is 

 grooved and a low" carina is developed on the anterior face. It 

 differs from D. dividum in that the neural spine (pi. 5, fig. 1) is 

 proportionately longer; the inferior transverse processes (pi. 14, No. 

 19) are also longer and are directed more obliquely backward. In 

 Sotalia the neural spine of the coossified axis and atlas is excessively 

 enlarged and is directed more backward than upward, projecting 

 above at least four of the succeeding cervicals. The shape of the 

 neural canal and the proportions of the anterior articular facets 

 can not be determined at present. It was possible to determine, how- 

 ever, that the centrum is not as high as in D. dividum and the neural 

 canal is relatively shallower. The postzygapophyses have nearly 

 horizontal articular surfaces and are situated nearly as high up as the 

 top of the neural canal. The odontoid process is very similar in shape 

 and proportions to that of Z>. dividuin. The transverse processes 

 are directed obliquely backward and outward and are much larger 

 and longer than the corresponding processes of the atlas. They are 

 deep vertically, rather thin anteroposteriorly, and the extremity is 

 obliquely truncated in two directions. There is a longitudinal carina 

 on the interior face of the axis and corresponding depressions on 

 each side. 



Third cervical. — The centrum of this cervical is not visible as it 

 has been forced out of its normal position in the series into the 

 neural canal of the axis. The zygapophyses and a portion of the 

 neural arch are all that are exposed on the right side. The position 

 of the remainder was determined by probing. The superior trans- 

 verse process is slender, with a small elliptical vertebrarterial canal 

 at the base. The inferior transverse process (pi. 14, no. 20) on the 

 left side is slender and more than twice as long as that on the fifth 

 cervical. 



Fourth cervical. — The centrum of the fourth cervical (pi. 14, no, 

 ^1) is thin, the neural arch is rather broad at the base, and the spine 

 is very low. The inferior processes are slender and are shorter 



