PETERSON: A REVISION OF THE ENTELODONTIDA 107 
the ribs are broad, with compressed sessile heads, and large tubercles, which are 
separated from the heads by deep cavities in the same manner as in Archwothervum. 
The fragments of the posterior ribs indicate that they were perhaps proportionately 
Fia. 65. (1) First Rib ; (2) Second Rib ; (3) Fifth Rib. From type of D. hollandi Peterson. } nat. size. 
broader than those in Archxotherium. In their relative lengths the ribs are not un- 
like those of the Oligocene genus, those behind being relatively perhaps somewhat 
longer. 
STERNUM. 
There are six sternebree present in the type. ‘The structure of the sternum is 
unique and can hardly be compared with that of the Suide. The presternum has 
an unusual vertical diameter, it is compressed transversely and the side view pre- 
sents an irregular and curious outline. 
The superior border of the presternum is slightly concave and terminates in 
front in a heavy and rugose tubercle ; anteriorly the bone is strongly emarginate, 
producing the superior tubercle which has just been mentioned and an additional, 
larger, inferior tubercle (see No. 1 in fig. 66). Ventrally the bone again has an 
emarginate border which terminates posteriorly in a rapidly expanded, truncated, 
and very rugose process. ‘The contact for the succeeding segment continues, from the 
truncated process mentioned, obliquely forward and upward and terminates in a 
slightly enlarged area which forms the contact for the second pair of ribs. The 
attachments for the first pair of ribs are situated on the lower half of the bone, 
nearer the anterior than the posterior border. In Archxotheriwm ingens the pre- 
sternum has the same general outline as in Dinohyus, but the borders, especially the 
