SHUFELDT : OSTEOLOGY OF THE STEGANOPODES 133 



starting, in some instances, from minute foramina found upon its surface. This 

 venation is but feebly marked in S. piscator. 



A lacrymal is a free bone, articulating with a roughened facet of some extent be- 

 neath the an tero- external angle of the frontal above, and by a smooth, gliding facet 

 on the upper side of the maxillary, which latter bone is thickened in a perpendic- 

 ular direction and otherwise enlarged in order to offer it the proper amount of sur- 

 face. As for the bone itself, it is of rather a columnar form, with the exception of 

 its extended anterior margin, which is roundly notched and shows on its inner side 

 the large pneumatic opening leading to its hollow interior. In S. cyanops this notch 

 is extended as a groove entirely across the outer face of the bone, and the pneu- 

 matic foramen is seen in this groove. 



In Gannets there exists, projecting horizontally from the outer margin of the 

 frontal bone, on either side, from its " prefrontal process," a few millimeters posterior 

 to the fronto-lacrymal suture, a small rounded ledge of membrano-cartilage, which 

 reminds one of the horizontal portion of the true lacrymal bone in certain gallina- 

 ceous birds, as the Perdicinse, for example. This feature has been studied by me in 

 Sula brewsteri and S. gossi, recently killed specimens for which I am indebted to 

 Mr. E. J.' Reed of Guaymas, Mexico, who kindly collected them for me. This 

 membrano-cartilaginous process probably never ossifies in the Sulidse. 



In the adult bird it is impossible to distinguish the exact position, or any of the 

 borders, of the nasal bone. 



The maxillo-jugal bar shows very plainly the suture between the jugal and 

 quadrato-jugal ; the latter is much smaller than the other portion, and shows a 

 strong peg-like process upon the inner aspect of its posterior end, which is about at 

 right angles to. the axis of the bone. It fits in the deep conical socket on the side 

 of the quadrate. Beyond its enlargement for the lacrymal the maxillary is a thin, 

 horizontal plate of bone, anchylosed in the usual way at its anterior end. Here it 

 really enters into the apparatus of the cranio-facial hinge. An ossicle having the 

 appearance of a process pointing backward and apparently coming from the pre- 

 maxillary is seen over this horizontal plate of the maxillary on either side. Pro- 

 fessor Parker found this condition present also in another species of Sula, and this 

 eminent anatomist apparently describes this ossicle as a " post-maxillary " for those 

 birds. Either rudimentary or better developed, it is probably present in one form 

 or another in all of the Sulidee. 



The interorbital septum, which is a thin, smooth plate, shows considerable of a 

 fenestra near its middle, and a few such openings of a very much smaller size pierce 

 its posterior wall in S. bassana. 



