SHUFELDT : OSTEOLOGY OF THE STEGANOPODES 189 



Posteriorly its wall is composed of compact tissue, being at right angles to the 

 longitudinal axis of the skull. It slants from the under side of the cranio-facial 

 hinge to the anterior margin of a median foramen, seen just anterior to' the keel 

 which is formed by the union of the palatines behind. 



This posterior maxillo-palatine wall has a cleft in its lower two thirds, while two 

 conical pits, placed side by side, lined with compact osseous tissue, occupy its upper 

 third. They have their bases opening in the rhinal chamber, and their apices are 

 pierced by the small subcircular nostrils, one in each conical passage. 



The hinder half of the jugal bar is compressed from side to side, slightly dilated, 

 with its end crooked up, and in life simply bound to the upper and outer side of 

 the quadrate. 



The body of a lacrymal fuses completely with the cranial elements above, its 

 upper surface assisting in forming the smooth superfices of the frontal region. This 

 is also the case in P. sharpei (PI. XXVII., Fig. 37). From this portion it sends down- 

 ward and slightly backward a descending process. This is composed of a cylindri- 

 cal pedicel for its upper third and an antero-posteriorly compressed portion for the 

 lower two thirds. It fails to reach the maxillary, its tip remaining free just above 

 that perpendicularly compressed bar which passes immediately beneath it. 



The interorbital septum is entire, with the exception of a semicircular perfora- 

 tion, which is immediately in front of the aperture in the anterior wall of the brain- 

 case that gives egress to the optic nerves. 



Each olfactory has a small foramen in either orbit at its usual site; the track for 

 the nerve being a broad, shallow groove beneath the orbital vault. 



The mesethmoid is very deep ; its anterior border is sharp and thin. Commencing 

 in the aperture of the angle between the pterygoidal shafts, it is carried directly 

 upward and forward to the expanded portion beneath the roof of the cranio-facial 

 region, the edge meeting the median division of the maxillo-palatines. (For figures 

 illustrating the skull of the Brown Pelican see my memoir on the "Osteology of the 

 Tubinares and Steganopodes," Proceedings U. S. Nat. Museum, 1888, Vol. II., 

 pp. 311-315.) 



The lower fourth of this ethmoidal border is thickened and rounded for the 

 articulation of the palatine and pterygoidal heads. 



Coming, as usual, from the anterior apex of the basi-temporal triangle, the other 

 portion of the rostrum is decurved and meets the point referred to above in the 

 angle between the pterygoids, 



A quadrate is a very large bone with a broad, triangular process. Its mastoidal 

 head can hardly be said to be divided into two, as in most birds, for the division is 



