122 PROCEEDINGS OF THE NATIONAL MUSEUM vol. los 



CERVICAL VERTEBRAE 



Of the seven vertebrae normally comprising the cervical series 

 of a cetacean, only four (pi. 7) were found associated with the skull 

 and mandibles. No evidence of ankylosis exists on any of these 

 cervicals. 



The axis, the third to seventh cervicals, and the first and second 

 dorsal vertebrae of Lophocetus calvertensis are for the most part con- 

 cealed by matrix. The ventral surfaces of these centra are somewhat 

 eroded and only small remnants of the lower transverse processes are 

 preserved. All of these vertebrae are sufficiently complete, however, 

 to assist with the allocation of the cervicals of L. pappus. The dorsal 

 portions of the neural arches of the fourth to seventh cervicals of 

 L. calvertensis are fairly complete and are relatively narrower antero- 

 posteriorly than those of the Calvert Miocene porpoise. The antero- 

 posterior diameters of the centra of the fifth, sixth, and seventh 

 cervicals of this Calvert porpoise are likewise greater than those of 

 corresponding cervicals of the St. Marys porpoise. The fifth and sixth 

 cervicals of L. calvertensis agree with those of L. pappus in having 

 lower transverse processes, and the seventh seems to possess on each 

 side a single upper laterally projecting transverse process. 



Atlas: In general form the atlas (pi. 7, fig. 1) differs from that of 

 Eurhinodelphis cocheteuxi (Abel, 1931, pi. 19) in having vestigial upper 

 transverse processes, a broader and longer hyapophysial process, and 

 a wider neural canal. The reduction of the upper transverse processes, 

 the enlargement of the lower transverse processes, the greater antero- 

 posterior diameter of the roof of the neural arch (completely enclosing 

 the vertebrarterial canals), and the widened hyapophysial process 

 distinguish this atlas from that of Inia geqffrensis. The atlas of 

 LophocetiLS calvertensis resembles that of L. pappus in essential details, 

 but is slightly wider, the posterior facets for articulation with the axis 

 are considerably larger, the large vertebrarterial canals do not pierce 

 the roof of the neural arch and are bounded in part by the dorso- 

 internal edges of the anterior facets for articulation with the condyles, 

 and the roof of the neural arch is more strongly arched. 



The lower transverse processes are normal in size, truncated 

 obliquely at extremity, but only vestiges of the upper processes 

 persist. These lower processes are short, dorsoventraUy compressed, 

 and project downward and backward. The facets for articulation 

 with the occipital condyles are concave, broader above than below, 

 and separated ventrally by an interval of 11 mm. The roof of the 

 neural arch is not elevated medially, the anteroposterior diameter 

 near the low crestlike neural spine measuring 25.5 mm., and is pierced 

 on each side by a vertebrarterial canal. The posterior articular facets 



