SHUFELDT.] OSTEOLOGY OF THE EREMOPHILA. 633 
presents for examination, just below the mastoid process, a large, oval, 
pneumatic foramen; other of these openings may exist in the depression 
on the posterior surface of the body of the bone already described. 
The inferior surface of the basi-sphenoid is convex outward, and slopes 
away gradually into the rostrum, anteriorly. The external orifices of 
the Eustachian tubes are extremely minute, as are the foramina for the 
entrance of the branches of the common carotid to the cranium. As 
already intimated when speaking of the pterygoids, there are no ptera- 
pophysial processes. 
The external aperture to the cavity of the otocrane is an elliptical 
slit, 1.5 millimetres wide at its widest part, looking almost directly for- 
wards, its lower end being the innermost or nearest the median plane. 
The mastoid, however, does not extend so far forwards but that ina 
direct lateral view we may see, through the opening, the funnel-shaped 
internal orifice of the Eustachian tube. The stability of the ear cavity 
is here, as in many birds, highly enhanced by the presence of numerous 
osseous trabeculae, acting as struts and braces to its walls. 
An examination of the interior of the brain-case shows the fossz for 
the several cephalic lobes to be large—indicating a brain of good size 
for the bird. As already defined, the foramina for the first and second 
pairs of nerves are in each case single, and as a whole more or less oval. 
A constriction, however, takes place in their outlines at the middles, 
formed by the encroaching interorbital septum, so that, looking out of 
the cavity, the foramen in either case appears double, whereas a view 
from an orbit reveals the fact of there being but one opening in either 
case. The olfactory foramen is very large—in the dry cranium—the 
deficiency being made up by firm membrane in the living Lark. The 
minute openings for the carotids at the base of the pituitary depression 
are placed, as usual, side by side transversely. The posterior wall of 
the sella turcica is deeply notched. 
The longitudinal sinus is best seen along the superior and median 
crest, just before it arrives at the olfactory foramen. The middle fossa 
for the accommodation of the cerebellum is distinctly marked by long 
transverse concavities, admitting the ruge upon the lobe in question 
when the brain is in situ. With regard to the structure of this bird’s 
cranium, we may say that it is largely cancellated, the intermaxillary 
and petrosal approaching nearest the compact variety of bone; this fact 
lends to this part of the skeleton a great lightness, and well-prepared 
skulls of this Lark are very pretty objects. 
The most remarkable feature to be observed, however, is the great 
amount of separation between the tables of the vault of the brain cavity, 
being fully a millimetre, and in some localities more, the interspace being 
filled in by quite an open dipléic tissue. This condition we well know 
to be a striking feature in the anatomy of the Strigide, but here is a 
bird that has the same arrangement as well marked, we believe, for its 
size, as any Owl in the North American fauna. The outline of the base 
of the cranium in Hremophila approaches the sector of a circle, a figure 
more or less true in all birds, and here, as in most others, the greatest 
departure from that figure being a too great convexity of the subtending 
arc. The length of the radius represented by the middle line is 3.2 centi- 
metres, the intertympanic chord, including the bones, being 1.4 centi- 
metres. We will only mention here, in regard to the free osseous ele- 
ments of the sense capsules, that the sclerotals retain their usual form 
and arrangement, numbering in each eye from thirteen to fifteen. The 
attachment among them is rather firm, remaining as shown in PI. IV, 
Fig. 41, after a considerable amount of maceration. The ossicula auditus 
