PETERSON: A REVISION OF THE ENTELODONTID Ai oF 
more opisthoccelous. This vertebra is, except in these minor details, quite similar 
to the corresponding bone in Archxotheriwm. 
Second Dorsal Vertebra.—The neural spine of the second dorsal vertebra is 
higher than that of the first, but not nearly so robust. In relative proportions 
the spine agrees quite well with that of Archxotheriwm. The vertebra as a whole 
Fig. 45. Lateral and Posterior Views of Fie. 46. Lateral View Fia. 47. Lateral View 
First Dorsal of D. hollandi Peterson. } nat. of Second Dorsal of D. hol- of Third Dorsal of D. 
Size. landi Peterson. } nat. hollandi Peterson. } 
size. nat. size. 
differs in some important particulars from that of Archxotheriwm, viz.: the vertical 
diameter of the centrum is relatively greater, owing to the unusual development of 
the inferior keel; the anterior half of the keel is developed into a heavy and rugose 
tubercle, which projects well below the anterior face of the centrum; the prezyga- 
pophyses nearly meet in the median line, forming a narrow irregular emargination, 
while in Archxotheriwm they are more widely separated. The posterior face of the 
