650 R. W. SHUFELDT 
families, many species of which would possess the skeletal parts 
of the foot of a size and proportion quite like the one in this fossil, 
it will be appreciated how useless it would be to express an opinion 
_as to the family this bird represented. No such attempt will be 
made here._ 
My reasons for creating a new genus for it are set forth on a 
foregoing page of this article. 
Yalavis (Yale and avis; the University at New Haven, Conn., 
U.S.A.; and avis, a bird). 
The specific name tenuipes refers to the slender bones in the — 
foot of the specimen, as seen in its fossil remains. 
Early in the summer of 1913, Mr. Theo. D. A. Cockerell, of 
the University of Colorado (Boulder, Colo.), when on a visit to 
Washington, handed me the specimen, here reproduced natural 
size in Fig. 3, for a description and, if possible, a diagnosis. 
As the specimen is very small, I had it enlarged, and this latter 
is reproduced in Fig. 4. 
It has no special history beyond having been collected in 1898 
at Florissant, Colo. 
At first glance, it has the appearance of being the fossil remains 
of some small bird, or even medium-sized bird, as it is associated 
with a few feathers. The latter consist of down (?), contour 
feathers, and one feather from a wing. The bones, whatever they 
may be, are in pazrs, and evidently not materially disturbed. 
By the aid of a two-inch objective on a powerful microscope, 
I brought these up to a large size for critical examination. To 
some extent they appear as though they might be a pair of coracoids 
and some part of the sternum; but as here exposed, I find that this 
suggestion cannot be verified. 
It may be some part of a bird’s skull; the smaller pair of bones, 
pterygoids, and the larger ones—partly exposed—palatines; but I 
doubt it. And were this so, the feathers would probably have 
belonged to the kead—a fact militated against by the presence 
of what is undoubtedly a wing-feather. 
These bones may have belonged to some other animal than a 
bird, or it may even have been some invertebrate form (crustacean), . 
and the association with feathers entirely coincidental, as we would 
