ART. 19 A MIOCENE PORPOISE FROM MARYLAND KELLOGG 47 



anteroposterior diameter of the neural spine near the base (16.7 

 mm.) is more than half the maximum diameter (28.4 mm.) at the 

 extremity. The metapophyses are knoblike processes which project 

 beyond the anterior epiphysis ; they are carinate externally and their 

 dorsal margins are at least 20 mm. above the top of the centrum. 



Tenth caudal. — The neural spine (pi. 1, fig. 1) is broken above the 

 level of the metapophyses and its extremity is missing. A large 

 portion of this caudal is still hidden by the matrix. The height of 

 the neural canal posteriorly is 6 mm. The enlargement on the pos- 

 terior border of the neural spine about halfway between the ex- 

 tremity and the level of the metapophyses is the most unusual 

 peculiarity. The minimum anteroposterior diameter of the neu- 

 rapophysis is approximately the same as the minimum diameter of 

 the neural spine. The inferior descending processes on which the 

 posterior facets for the chevron are borne are thicker than those on 

 the seventh caudal, but unlike those on the eleventh are not joined 

 with the processes of the anterior facets by a continuous lamina of 

 bone. The transverse processes are short, subtriangular in outline, 

 and the distance from the foramen at the base to the anteroexternal 

 angle is 16 mm. 



Eleventh caudal. — The neural spine (pi. 13, fig. 1) is fractured at 

 the base, but otherwise this caudal is practically complete. It is 

 characterized by very short triangular transverse processes, a small 

 neural canal, a short neural spine, and small metapophyses. The 

 minimum anteroposterior diameter of the neurapophysis (19.5 mm.) 

 is considerably greater than the minimum diameter of the neural 

 spine (13.8 mm.). The height of the neural canal posteriorly is 

 4.5 mm. The paired descending processes on which are situated 

 the posterior facets for the corresponding chevron are continuous 

 anteriorly with those for the preceding chevron. The thin lamina of 

 bone which connects these processes is perforated mesially by an 

 elongate foramen. The distance from the foramen at the base of the 

 transverse process to the anteroexternal angle is 13.5 mm. The 

 lateral surface of the centrum is traversed obliquely by a broad 

 groove which extends from the po.sterior margin of the neural arch 

 to the above-mentioned foramen. 



Ttoelfth caudal— This caudal (pi. 13, fig. 2) is complete. The 

 centrum is rather deep but is narrow transversely. The paired 

 descending processes on which are situated the posterior facets for 

 the corresponding chevron are swollen, occupying more than half 

 the length of the centrum, continuous anteriorly with those for the 

 preceding chevron, and are pierced mesially by a foramen of medium 

 size. From this foramen a short broad groove extends upward to 

 the inferior orifice of the lateral vertebrarterial canal. About 7.5 



