40 PKOCEEDINGS OF THE NATIONAL MUSEUM vol. CD 



tionately larger and broader, the neural canal is lower, and the dia- 

 pophyses are shorter. 



Fifth dorsal. — In general appearance this vertebra is very similar 

 to the fourth. The centrum (pi. 14, no. 29) is longer than that of 

 the fourth and is more noticeably constricted from side to side near 

 the middle. Both epiphyses are attached to the centrum. The neu- 

 rapophyses are more highly arched than on the fourth. The meta- 

 pophyses are broader than on the preceding dorsals and the dia- 

 pophyses are shorter. The neural spine is similar in outline to that 

 on the fourth dorsal. Compared with the same vertebra of Del- 

 phinodon dividum, the neural arches and neural spine are relatively 

 wider anteroposteriorly. 



Sixth dorsal. — The centrum is almost as long as broad and the 

 neural spine is somewhat wider anteroposteriorly. The centrum is 

 so strongly constricted that an indistinct ventral carina is developed. 

 Both epiphyses are attached to the centrum. The mesial dorsoven- 

 tral constriction of the diapophyses has disappeared. On the first 

 six dorsals there are distinct facets on the posterosuperior lateral 

 borders of the centra for the capitula of the following ribs, but they 

 are not developed on the seventh and succeeding dorsals. This indi- 

 cates that there were not more than seven pairs of double headed 

 ribs. 



Seventh dorsal. — This vertebra differs very little from the sixth. 

 The centrum (pi. 14, no. 31) is slightly longer than broad, distinctly 

 constricted near the middle, and the tips of the metapophyses are 

 directed upward. The facet on the diapophysis for the tuberculum 

 is subtriangular in outline and the whole process projects at a slightly 

 lower level than on the preceding dorsal. The neural spine is 

 slightly constricted below the extremity. On the first seven dorsals 

 the bases of the neural arches extend practically the full length of 

 the centrum, but on the eighth, ninth, and tenth dorsals they have 

 receded from the posterior epiphysis. Both epiphyses are loose and 

 project laterally beyond the centrum on the left side. 



Eighth dorsal. — There is no transitional dorsal with closely approxi- 

 mated facets for the tuberculum and capitulum of the correspond- 

 ing rib on the side of the neural arch as in Eurhinodel'phis and many 

 of the living delphinoids. On the eighth dorsal (pi. 14, no. 32) of 

 this fossil porpoise, however, there is a single facet which is placed on 

 the extremity of a short diapophysis. The distance from the inside 

 margin of the neural arch to the tip of the diapophysis is 16.5 mm. 

 The diapophyses project laterally from the neural arches at a con- 

 siderably lower level than on the seventh dorsal. There is a notice- 

 able increase in the length of the centrum. Both epiphyses are at- 

 tached to it. The neural spine is wider anteroposteriorly than on the 



