ENDOCRANIAL ANATOMY OF FOSSIL MAMMALS 365 
anterior, it rounds the pyriform lobe and appears on the lateral 
surface in the floor of the sylvian fossa. Running within the 
sylvian fissure, it meets the middle meningeal rami near the 
ectosylvian sulcus, and from that point the course of the artery 
is obscure. 
The venous dural sinuses are not particularly worthy of note, 
since they present no unusual features; but emptying into the 
superior sagittal sinus are cerebral veins. A pair of these of 
unusual size and prominence is shown in figure 13. These lie 
just posterior to the ansate sulcus. 
Artiodactyla 
Oreodon (Merycoidodon) culbertsont Leidy.. Since Davidson 
Black (’20) has described so fully the endocranial anatomy of 
Oreoden, with a reconstruction of the brain, little further need 
be added here concerning the general nature of this interesting 
pig-like ruminant. I have, however, shown in figures 22 and 
23 the dorsal and ventral views of a well-preserved cast of this 
animal, which is rather unusual in showing very nicely the model- 
ing of the cerebrum, both above and below. In general the sulci 
are similar to those described by Black (’20) and their condition 
is shown in figure 22. This brain shows an unusual development 
of the dural sinuses, the sagittal (Sin.sag.) and the infero-lateral 
(Sin.t.lat.). This cast is further unusual in presenting the 
olfactory bulbs, a portion which is often lost in endocranial casts 
of this animal. Length of cerebrum, 40 mm.; width, 38 mm.; 
width of olfactory bulb, 5 mm. 
On the base the tuberculum olfactorium is rounded and well 
marked. The pituitary elevation is evident as an elongated 
elevated mound between the large rounded areae pyriformes. 
Save for the general shape of the cerebellum, nothing can be told 
of this region. This cast displaces 41 ec. of water. 
Oreodon gracilis Leidy. Another cranial cast doubtfully 
assigned to Oreodon gracilis is shown in figures 18, 19, and 20. 
The cast is small when compared to another cast of the same 
species, but the sulci are well developed. The entire endocranial 
cast measures 60 mm. in length. The cerebrum is 36 mm. long 
