A NEW FOSSIL PORPOISE FROM MARYLAND. 179 



superior lateral borders of the centra for the articulation of the heads of the 

 ribs. The anterior and posterior faces of the centra of the 1st and 3d thoracieg 

 are elliptical, but those of the vertebrae farther back are cordate, or shield- 

 shaped. The inferior surface of the centrum is rounded in the 1st and 3d tho- 

 racics, flat in the 4th, rounded in the 5th, and somewhat angular in the vertebrae 

 farther back. 



In addition to the foregoing general description, it seems desirable to record 

 certain special features of individual vertebrae. 



1st Thoracic (PL XX, fig. 1 ; PL XXI, fig. 1 ; PL XXII, figs. 1 and 7).-This ver- 

 tebra has the general appearance of the seventh cervical of varioi^ recent delphi- 

 noids, but has a distinct facet for articulation of the tubercle of a rib. The centrum 

 is about one-fourth as thick as broad, the anterior face concave and the posterior 

 convex. The epiphyses are extremely thin, being scarcely more than 1 millimeter in 

 thickness. There is a distinct oval facet for the articulation of he head of tho 

 second rib on the postero-superior lateral margin of the centrum. The neural 

 arch is low, broad and quite thin, with a lateral process similar to itself on each 

 side, which bears the facet for the articulation of the tubercle of the first rib. This 

 facet is irregularly oval, and rather narrow. The anterior zygapophysis is 

 elliptical, flat, very narrow, and directed upward. The posterior zygapophysis 

 is similar but much larger, broader and concave, and is directed downward and 

 a little inward. The spine is lacking, but was probably very short. 



Compared with the same vertebra in Phoccena, the principal differed s are 

 as follows: The centrum is more distinctly elliptical. The neural canal is much 

 larger. The neural arch and transverse process are broader, thinner and less 

 elevated, and upper border of the latter becomes nearly vertical, instead of 

 horizontal. The facet for the articulation of the tubercle of the rib is narrow and 

 elongated and directed downward, while in Phoccena it is nearly round and 

 directed outward. The posterior zygapophyses are directed downward, rather 

 than obliquely outward. 



3d Thoracic (PL XX, fig. 2; PL XXI, fig. 2; PL XXII, figs. 2 and 8).— This 

 vertebra, with the epiphyses, is nearly half as thick as broad. The spine is erect 

 and tapering and the metapophyses horizontal and directed a little forward, 

 having a large oval articular facet at the end. Both anterior and posterior faces 

 of the centrum are concave. This vertebra may possibly be the 2d thoracic, 

 but as it does not fit well with the first, I am disposed to regard it as the third. 



Compared with the same vertebra in Phoccena, the centrum is broader, 

 more elliptical, and less elongated antero-posteriorly. The neural spine is 

 vertical, instead of somewhat inclined backward. 



4th Thoracic (PL XX, fig. 3; PL XXI, fig. 3; PL XXII, figs. 3 and 9) .—The 

 centrum of this vertebra, with the epiphyses, is more than one-half as long as broad. 

 The anterior and posterior faces of the centrum are only slightly concave. The 

 epiphyses are about 2 mm. thick. In most respects this vertebra is similar to 

 the last. The spine, however, which is detached, appears to be a little recurved 



