a 
ARTIODACTYLA. 
Great diversities are found in this order, especially between the suilline 
and ruminant divisions. In the former, with the exception of the Hippo- 
potamide, there are no foramina; in the Ruminuntia they are more nu- 
merous than in any other order cf the class. The Ruminantia are, like the 
equine Perissodactyla, characterized by the presence of the supraglenoid 
foramen ; to this the Camelidew and, some others add the mastoid. The 
Tragulina must be excepted from this rule, for they have nothing but the 
postglenoid. 
Omnivora. 
Sus, Dicotyles and Phacocherus ; no foramina. ; 
Hippopotamus and Cheropsis; postglenoid, postsquamosal, mastoid 
. and a rudimental supraglenoid. 
Ruminantia. 
Tragulus ; postglenoid only. 
Oreodon ; postparietal and mastoid. In one specimen of 0. culbertsont 
from Colorado, I find a minute supraglenoid on each side ; in other speci- 
mens it is wanting. : : 
Poébrotherium, postparietal, postg:cndid ; mastoid ; a small supraglen- 
oid. 
Fra. 6.—Skull of Procamelus occidentalis Leidy, Loup Fork of New Mexico; 
one-fourth natural size; showing supraglenoid foramen, SPG. 
Procamelus, Camelus, Auchenia ; postglenoid, supraglenoid and mastoid. 
Bos ; postglenoid and supraglenoid only. 
Antilocapra ; postparietal, postglenoid, mastoid, and a large supraglen- 
oid. ; 
Giraffa ; pos'glenoid, supraglen@id, postsquamosal and mastoid. 
Oreas, Ovis, Cervus; postglenoid, supraglenoid, postsquamosal, postpa- 
rietal and mastoid. 
From the preceding the following conclusions may be derived : 
(1) The sinous foramina furnish valuable diagnostic characters, and 
may, with proper limitation, be used in systematic definition, 
(2) The primitive condition of the various maminalian orders appears 
to have been the possession of a limited number of these foramina. 
