1006 
Journal of Agricultural Research 
Vol. XXVIII, No ID 
to classify with precision. In the majority of individuals the shelf is squarish 
in general outline, there being a slight medial notch flanked upon either side 
by a minute process, often spinous. These processes, however, are sometimes 
lacking, and the notch varies in size, at times being entirely absent, so that the 
shelf is then practically unbroken in outline. In a few examples the entire 
anterior portion of the interpterygoid fossa gradually tapers to a point. This 
variation is not dependent upon age but is entirely individual. The lateral shelves 
of the palatines (antero-lateral to the fossa) are also quite variable in exact 
configuration, probably being largely influenced by the development of the 
internal pterygoid muscles. The depth of the palatal pits also varies individually 
to a great extent, though not relatively with age. Finally, the entire palatal bone 
is pierced by many minute foramina and studded with tiny pits, no two being 
precisely alike in this respect. Hence, it is seen that individual variation in 
the palatal region is so great and of so intangible a nature (the several types 
being so inextricably blended) that these characters can be used only after careful 
deliberation. 
Frontals. —The suture between these paired bones is clearly distinguishable 
in juveniles, but has disappeared by the time that the animal has attained sexual 
maturity. Each frontal articulates with the parietal, squamosal, alisphenoid, 
maxilla, premaxilla, lachrymal, and nasal. The posterior portion is characterized 
by great individual variation caused chiefly by the position of the squamoso- 
frontal suture. The posterior point of this may be either lateral or medial to 
the margin of the interorbital constriction; or in other words, it may be situated 
at either the lateral or medial edge of the anterior projection of the parietal. 
Most of the other sutures vary but slightly, and there are no age differences 
save that in juveniles the irregularities of the bone are more poorly defined and 
less abrupt. There are some individual differences anteriorly, but these are 
discussed elsewhere. 
The chief interest in this pair of bones lies in the interorbital region. The 
only variation in the width of this, measured at its narrowest portion, is individual. 
Not only is it actually just as great in young animals, but may be greater, while 
among the examples with narrowest interorbital are some of the largest adults. 
In normal males this averages 3.84 mm., with extremes of 4.1 and 3.6, a difference 
of 0.5 mm., or 13 per cent. In females, the average is 3.77 mm., also with extremes 
of 4.1 and 3.6, a difference of 13.3 per cent of the average. 
Normally there are two interorbital ridges, these being in reality anterior 
extensions of the temporal ridges and terminating at the postero-lateral edges 
of the nasals. They are absent in the smallest juveniles, though definable in 
large juveniles and practically all older individuals. In a very few, however, 
they are to all intents absent. There is great variation in the degree of defi¬ 
nition in these ridges, as well as in the distance between them and all other 
details. There is a tendency for them to coalesce with advancing age, with 
consequent elimination of the intervening sulcus. Most, but not all, of the 
largest adults thus have single interorbital crests. Similarly, the sulcus is quite 
wide in many of the smaller subadults, though narrower in the majority, while 
it is well-nigh obliterated in a few, even of those that are barely sexually mature. 
The writer is led to believe that in those large adults now having a sulcus the 
latter was of unusual width in their youth, and vice versa. Animals with a 
tendency toward coalescence of the ridges usually show indications of a strong, 
angular braincase. But, on the other hand, this is not the case in the indi¬ 
viduals of such a large minority that one hesitates at reaching any definite de¬ 
cision as to cause. Males are somewhat more heavily ridged in this region 
than are females. 
