38 NEW YORK STATE MUSEUM 



is in any other representative of the family. The general internal 

 surface is very smooth and rounded, there being not even any 

 median indication of the position of the keel. 



All of the borders of the sternum are sharp and thin, except the 

 anterior moieties of the lateral ones, and these are more (Gym- 

 nogyps) or less (Cathartes) occupied by the facets for the sternal 

 ribs. These latter are small parallelograms, varying in size accord- 

 ing to the rib they support, being placed transversely and tipped 

 slightly outward, and separated from each other by subelliptical 

 depressions that show the pneumatic openings at their bases. Upon 

 its pectoral aspect the body of the sternum is likewise smooth, and 

 presents for examination the prominent pectoral ridges, on either 

 •side, which originate in eminences in the middle of the costal 

 borders to 'be produced backward and terminate just anterior to 

 the midxiphoidal prolongation at the base of the keel. This latter 

 is very deep and strong in all of the Cathartidae; commencing, as 

 it does, below and within the manubrial prominence, it extends to 

 the extremity of the sternal body behind. Its anterior margin is 

 always thickened, as is its inferior border in Gyparchus and the con- 

 dors. A well marked muscular line is found on either side of the 

 keel, a few millimeters within its inferior boundary, extending from 

 the carinal angle to be gradually lost before arriving at the posterior 

 termination of this part of the sternum. It is less distinct in 

 Gyparchus and the condors. 



There is no exception among the Cathartidae to the fact that the 

 xiphoidal end of the sternum exhibits a number of patterns for the 

 same species ; a circumstance that may be due to slight differ- 

 ences in age, but which, nevertheless, detracts from the reliability 

 of this bone as a structure upon which to base classificatory indi- 

 cations. When we come to examine a sufficiently large series of 

 sterna from any species of the Cathartidae, it will not appear 

 strange to us that the figures of this bone, as presented to us by 

 different workers, never appear to agree in outline, any more than 

 do their written descriptions of the sterna of these vultures. 

 This is due, as we have just remarked, to the variations to be seen 

 in the notches and foramina of the hinder portion of the body of 

 the bone ; but more especially the foramina, and the notching is 

 pretty constant for any particular species. This variation is ex- 

 tended to the Old World vultures, as well as to many of the true 

 Falconidae. 



