126 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol. YI. 



the inner and posterior one, surmounting the shorter limh or bifurcation, 

 looks backwards and upwards. These two projections of the mastoid 

 process are further separated posteriorly by a deep non- articular de- 

 jDression. The orbital process is well developed, long and slender, ter- 

 minating in a knobbed extremity, the whole extending well within the 

 orbital space. It has at its base, internally, the facette for the ptery- 

 goid already alluded to. This process is subcompressed from before 

 backwards, and has throughout a gentle curvature upwards, having 

 much the form of the thorn of the common rose, without its sharj) point. 



There are two articular facettes on the inferior side of the mandibular 

 €nd, divided by rather a deep depression. Of the two, the inner is the 

 larger and more symmetrical in form, being transversely elliptical. The 

 outer one seems to be borne on rather a constricted neck, having on its 

 outer aspect the acetabulum for the hemispheroidal facette on the squa- 

 mosal. The anterior surface of the body is smooth and triangular in 

 outline 5 the opposite and inner surface, somewhat similar in appearance, 

 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 hasi-splienoid 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 i)art, looking almost directly for- 

 w^ards, its lower end being the innermost or nearest the median j)lane. 

 The mastoid, however, does not extend so far forwards but that in a 

 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 trabeculse, acting as struts and braces to its walls. 



An examination of the interior of the brain-case shows the fossae for 

 the several cephalic lobes to be large — indicating a brain of good size 

 for the bird. As abeady defined, the foramina for the first and second 

 X)airs 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 i)osterior wall of the 

 sella turcica is deeply notched. 



