MIOCENE PORPOISES — KELLOGG 123 



(pi. 7, fig. 5) are subovoidal in outline, convex from side to side, 

 slightly concave dorsoventrally, and are set off from the posterior face 

 of the centrum by distinct margins. The hyapophysial process is 

 rather large, flattened dorsoventrally, and noticeably rugose dorsally 

 along lateral and hinder borders. On the dorsal surface of the hyapo- 

 physial process, and at the base of the somewhat pyriform neural canal, 

 there is a concave heart-shaped facet for articulation with the odontoid 

 process of the axis. 



For comparison, the measurements, in miUimeters, of the atlas of 

 Lophoceius calvertensis are as follows: Greatest distance across atlas 

 between outside margins of anterior articular facets, 93; across pos- 

 terior facets, 96.5; distance across atlas between tips of transverse 

 processes, 121 -f; and greatest transverse diameter of neural canal 

 anteriorly, 38. 



Fifth cervical: Unlike the fifth cervical of Inia geqffrensis, 

 this vertebra (pi. 7, fig. 3) lacks the downwardly projecting, elongated, 

 and rather robust lower transverse processes. It is distinguished 

 also by the fusion of the thin upper transverse process with the 

 thicker lower one, completely enclosing on each side the large verte- 

 brarterial canal, and by downward projection of the short ventrally 

 directed process that arises near the base of the lower transverse 

 process. The centrum is rather thin (16 mm.), the dorsal portion 

 of the slightly elevated neural arch is narrow, and the neural spine is 

 reduced to a low crest. The prezygapophysial facets slope obliquely 

 downward from outer to inner margins. The postzygapophysial 

 facets are rather large, and are placed obliquely on the postero- 

 superior border of the pedicle of the neural arch. 



Sixth cervical: The transverse processes of this cervical (pi. 7, 

 fig. 2) are incomplete distally but otherwise are well preserved. The 

 enlargement and elongation of the lower transverse processes at once 

 distinguish this vertebra from that of Inia. The upper transverse 

 process apparently tapered to a thin distal end and may have partially 

 inclosed the large lateral vertebrarterial canal. The lower transverse 

 process is directed downward and backward but exhibits an irregular 

 conformation, although somewhat flattened dorsoventrally and 

 expanded near extremity. The centrum is slightly thicker than that 

 of the fifth cervical. The prezygapophysial and postzygapophysial 

 facets slope obliquely from outer to inner margins. The neural 

 spine is a low crest, and the dorsal portion of the neural arch is 

 slightly elevated. 



Seventh cervical: In contrast to the sixth cervical, the antero- 

 posteriorly flattened transverse processes (pi. 7, fig. 4) are directed 

 outward from the dorsal half of the lateral face of the centrum and 



