188c.l PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 315 



subcireular openings to the nostrils, situated a little beyond the irreg- 

 ular lino marking the cranio-facial hinge. (Fig. 43.) 



Their centers are about 2 cm apart, and each oue is situated at the 

 posterior end of a groove. These grooves extend the en lire length of 

 the superior mandible, passing out on either side of the hook at its an- 

 terior extremity. At first each is rather on the lateral aspect of the 

 bone, but beyond the posterior half they gradually converge and get on 

 top, to include between them the prominent convex culmen. Just be- 

 fore reaching the hook, however, the included surface becomes flat and 

 depressed, when the lines terminate, as pointed out above. 



Fig. 43 shows the form and direction of the cranio facial line, and also 

 the broad, smooth surface of the top of the skull in this Pelican. This 

 is very flat for the frontal region, being simply curved downward at the 

 outer borders. As we proceed backward to the parietal region, how- 

 ever, it gradually becomes more convex and dome like, though still re- 

 taining its absolutely smooth and polished character. This latter may 

 also be seen from a posterior aspect, and below it the high, arching, and 

 equally smooth occipital area. This latter extends down on either side 

 over the enormous mastoidal elevations of this bird. We also notice 

 that from this view we may see directly into the foramen magnum ; the 

 entire pterygoids are in sight, and the quadrates come down far below 

 the basi cranial plane. 



The mandible from the skeleton of a Pelican is represented by a long, 

 narrow loop of bone, which is strikingly devoid of prominent characters. 

 Its symphysis is very short and decurved, beiug slightly excavated on 

 its superior aspect behind. 



The upper and lower margins of either ramus are rounded for their 

 entire length, while the sides included between them become gradually 

 narrower as we proceed in the direction of the symphysis. These are 

 smooth both internally and externally and both concave in the vertical 

 direction. 



Rather more than the posterior moiety of each ramus is hollow for 

 the admission of air, and each presents two foramina, which seem to 

 be intended for that purpose. One of these is on the inner and upper 

 aspect of the ramal shaft, just beyond a concavity that occurs immedi- 

 ately anterior to the articular cup. The other, elliptical in form, is on 

 the inner and lower aspect, and about 2 cm beyond it. 



Bach articular cup presents two concavities— a central one and another 

 occupying the inturued process of this extremity. Both have pneu- 

 matic foramina at their bases. The mandibular angle behind is trun- 

 cate and much compressed in the perpendicular direction. The under 

 surface of one of these ends is perfectly smooth and gradually merges 

 into the inner and outer surface, of the ramal shaft. Almost complete 

 disappearance of the coronoids has taken place. Both the skull and its 

 mandible are highly pneumatic. 



