OSTEOLOGY OF BIRDS 



13 



just been made, extends backward to meet the ethmoid in Ca- 

 thartes a. septentrional is and Catharista urubu, 

 and in all the species spreads out more or less laterally, 

 thus forming a strong abutment superiorly, while it divides 

 the space into two, so that they appear like true longitudinal bony 

 nostrils within. In all the vultures examined, with the exception of 

 Gymnogyps, a pit is seen to exist upon the inferior aspect of the 

 horizontal partition, in the middle line, it having almost the appear- 

 ance of a pnenmatc foramen to supply this part of the skull. 



All of the Cathartidae have skulls of a characteristic appearance 

 when viewed upon superior aspect. Old birds, as a rule, exhibit a 

 transverse though moderate mounding of the frontal region im- 

 mediately posterior to the craniofacial depression, and posterior to 

 this the interorbital area is very broad. The cranium in the parietal 

 region, and all down* at the sides is regularly rounded and smooth. 

 It presents evidence of a good brain case within. The surface ex- 

 hibits, further, many osseous venations, the majority of which run 

 to the foramina that exist in an irregular double row, removed by a 

 few millimeters from the orbital peripheries. These foramina lay 

 along in a shallow groove in these localities. From them the bony 

 and sharp edged brows overhang the orbital cavities which are 

 rendered especially deep by such beetling eaves. Age has every- 

 thing to do with the extent to which the frontal bones thus extend 

 out laterally and overarch the orbits above. Specimens of young 

 and adult Cathartes a. septentrionalis demonstrate 

 this most conclusively, and as another good instance I have -two 

 crania of Gymnogyps before me ; in one, the superior orbital peri- 

 pheries are jagged and thin, coming very close to the foramina men- 

 tioned in the last paragraph, being only a little over two centimeters 

 apart, measured at the narrowest point transversely across the 

 frontal region. In the other specimen, and evidently a very old 

 bird, they are rounded and arched over the orbits, upon either side, 

 thick and heavy, their rims being nearly five centimeters apart, all of 

 which lends this skull a far more raptorial aspect than is enjoyed by 

 the skull of the younger specimen [see pi. 2, fig. 2]. 



Most prominent among the features at the lateral aspect of the 

 skull of these vultures of ours, is the large lacrymal bone already 

 alluded to in part. We have sufficiently pointed out how its anterior 

 border above articulates in a peculiar manner with the nasal, and 

 how the bone fuses with the frontal. Now below this, upon its 

 lateral aspect is a longitudinal groove, and still inferior to this again, 

 the main descending portion of the bone. This, in old specimens of 



