A NEW FOSSIL PORPOISE FROM MARYLAND. 



177 



corresponding furrow. The neural canal is large and oval. The posterior 

 zygapophyses are salient, nearly horizontal, and situated nearly as high up as 

 the top of the neural canal. The odontoid process is only slightly produced 

 anteriorly, but bears on its inferior surface a large convex facet, which articulates 

 with a similar concave facet on the centrum of the atlas, as in Delphinapterus. 

 The single transverse process is much larger and longer than that of the atlas 

 It is oblong, broad vertically, and rather thin antero-posteriorly, the free end 

 blunt and rounded. The process is directed obliquely backward and outward. 

 Viewed from behind, the centrum shows the larger, rather concave surface for 



articulation with the third cervical, and on each side a broad, imperforate. 



concave surface ending in the transverse process. 



When the atlas is imposed on the axis, and the two vertebrae viewed from in 

 front, the parts visible very closely resemble in form those of Steno and other 

 delphinoid genera. When viewed from below, a notable difference is observable, 

 in that the transverse process of the axis is much longer than that of atlas, the 

 reverse being true in Steno and other recent delphinoids. 



3d Cervical (PL XIX, fig 



7,8) 



The 3d to the 7th cervicals are all ver> 



thin, as in recent delphinoids, and present substantially the same characters as 



found in such genera as Steno, Tursiop 



etc 



In the 3d. the centrum 



quite convex forward. The neural arch is very broad at the base, the neural 



canal nearly circular, and the spine only a few millimeters in height. The 



vertebr arterial canal is elliptical, with the principal diameter about 8 mm. It 



was probably completely surrounded by bone when the vertebra was intact. 



It is situated a little below the middle of the height of the centrum. 



4th Cervical (PL XIX, figs. 9, 10). — Only the imperfect centrum of this vertebra 



is preserved. The vertebrarterial canal appears to have been larger than in the 

 3d cervical. 



5th Cervical (PL XIX, figs. 11, 12).— This vertebra is nearly complete. It is 

 similar in form to the 3d, but the centrum is less convex anteriorly, and the 

 neural canal depressed elliptical rather than round. The vertebrarterial canal 

 was originally completely surrounded by bone, and had a diameter of about 

 1 1 mm. The outer slender portion of the ring was joined below to the superior 

 edge of an oblong transverse process about 7 mm. long which extends obliquely 

 downward and outward and a little backward. 1 



6th Cervical (PL XIX, fig. 13).— This vertebra is buried in the matrix under the 

 7th cervical in such a position that only the inferior transverse process, the ring 

 around the vertebrarterial canal and the neural arch and spine can be seen. 

 The inferior transverse process is large and inversely triangular, with the lower 

 portion directed backward, so that it appears concave from behind. It is about 

 14 mm. long and 13 mm. broad at the top. The vertebrarterial canal is larger 

 than in any of the preceding vertebrae and appears to have been completely 



1 The bony ring was traceable throughout while the vertebra lay in the matrix, but the parti 

 became separated when it was removed and could not be reunited in the natural position. It is not 

 shown, therefore, in PI. XIX, fig. 11. 



12 JOURN. ACAD. NAT. SCI. PHILA„ VOL.XV. 





