THE FOSSIL AVIFAUNA OF THE 
417 
In general form it has all the characters of the podal joint as seen in tlie 
Eagles now with us, and the fossil specimen is perfect. Until more material is 
forthcoming I have thought best to retain this species in the genus Aquila, and 
have bestowed upon it the specific name of pliogryps, composed r)f plio from plio- 
cene, and gryps, a griffin (Gr. ypu4'), convinced as 1 am that it was larger than a 
large Eagle, but from its more slender build, probably M'ith habits more like a 
Falcon, in which case it no doubt stood among the most dreaded of the raptorial 
birds during the time it flourished. (Fig. 33, PI. XVII). 
Equus Beds of Oregon ; Cope collection. 
Aquila sodalis sp. nov. 
This is another, and considerably smaller Eagle tliat co-existed with tlie last 
described one. Possibly it may have been the Aqtiila danana of Mansli, wliich he 
describes as “an extinct species of Eagle nearly as large as the modern (lolden 
Eagle”.' In the present collection it is represented by tlie proximal fourth of the 
left tarso-metatarsus, more or less imperfect. (See Fig. 33, PI. XVII). .Marsh's 
specimen of A. danana is described by him from the distal portion of a lel’t tibia ”, 
with “width of condyles in front” ecpial to eight lines. Now the greatest trans- 
verse width of the proximal end of the specimen in my hands alsso measums eight 
lines, or perhaps rather less. From this I am inclined to think that A. sodalis was 
perhaps a smaller bird than danana, and somewhat smaller than either the (lolden 
or White-headed Eagles. There is also in the collection the mesial third ol’ an os 
fiircida of a medium sized Eagle, and it also very likely belonged to an individual 
of the pi-esent species. Its characters are ([uitc like the characters of that part of 
\\\& os fw'ctdam any of the typical modern Eagles. In this connection I would 
say that there may be considerable specific variation in the form of the os furcula 
in any of the existing sjjecies of this group of the Accipitres. A. danana was di.s- 
covered in the Pliocene of Nebraska. 
A. sodalis had in the proximal moiety of its tarscHiietatarsus all the usual 
characters found in the present representatives of the genus Aquila. The tniKurle 
for the insei'tion of the tendon of the tibialis anticns mu.scles is stmngly pro- 
nounced, being rather to the outer side of the longitudinal mid-gr(M)ve on the 
anterior aspect of the bone. This tubercle is eight millimetres long, and sitnateil a 
little less than five millimetres below the two antero-i)Osterior perforating foramina 
found between it and the head of the bone. The inner one of these foramina 
appears behind, just at the louver point of commencement of the inner and largt*r 
process of the hypo-tarsus. In this last character it agrees with a specimen of //. 
leucocephahis at my hand. There is not sufficient material at my command to 
decide whether the posterior points of emergence of these foramina in the Eagles is 
constant or otherwise. 
To be of the best service our large Museums should have at least seven or 
eight skeletons of each species of our United States Eagles, and then the paloonto- 
^Marsh, O. C., Am. Jour. Sci. II, 1871, p. 125. 
