FOSSIL FEATHERS AND UNDESCRIBED FOSSIL BIRDS 651 
find the fossil bones of some small mammal mixed up with, or in 
the same matrix associated with, those of some large raptorial 
species of bird that had eaten it just prior to its death. Such a 
case I have recently had good reason to suspect. 
Pressure, fracture, and a number of other causes have caused 
fossil bones of animals of all sizes (vertebrates) to change their 
form and appearance. This must be borne in mind when making 
examinations of such material as we have here. 
Then, when incased in a matrix and only partially exposed, 
bones have a very different appearance from what they have when 
seen in entirety. Every paleontologist of experience is aware of 
this fact. 
Let us imagine that the fossil base of the superior mandible 
of a male surf scoter (Oidemia perspicillata) was the only part 
exposed in a dense matrix; would anyone suspect it of being a 
duck? When some bones are but partially exposed in the matrix, 
they often resemble others of the skeleton when the latter are more 
fully in view. For example, we may so far immerse the distal 
end of some avian humeri that the part left exposed may, in some 
instances, very much resemble the coracoid of some other kind of 
bird; and there can be no end to such instances. 
This may easily be the case with the specimen here being 
discussed. The larger pair of bones seen in the enlargement in 
Fig. 4 may be the proximal extremities of a pair of humeri, palmar 
aspects, and only partly exposed, and the small pair (?) below them 
some part of a dorsal vertebra. It is quite possible. 
In short, I am of the opinion that a reference—a correct ref- 
erence—cannot be made for this specimen, beyond its being 
probably bird, and under the circumstances it would be useless to 
give it a name. 
The fossil bird: bones from Silver Lake, Ore., mentioned in 
Dr. Schuchert’s letter on a previous page of this article, are, in 
all particulars, like those belonging in the Cope collection of the 
American Museum of Natural History of New York City. Very 
recently I have fully described that entire collection, and this 
description will appear as a bulletin of that institution with upward 
of 600 figures on plates. 
