180 Ornithichnites of the Connecticut River Sandstones. 
attention to the fact that the part depressed by the weight of the 
bird is so condensed as to appear to be enamelled, and is extremely 
hard. Hach tuberous joint presents the appearance of being 
swayed by a distinct blow rather than being moulded by a fleshy 
joint. In some examples there is no concavity in the depression 
of the individual joints, on the contrary the surface is flattened 
and may properly be illustrated by the impress of a hammer upon 
a mass of lead. [Nos. v1, xv to xvii, inclusive.]| The beauty 
and perfection of the impressions seem due to the condition of the 
plastic material at the time of receiving them, and the finest ex- 
amples are those in which the impressions are most superficial, 
being evidently made when the surface of the stratum had been 
subjected to a partial process of desiccation, just at that point suf- 
ficiently hard to take as well as receive the minutest lines. This 
peculiarity is very apparent in your collection; in some of the 
specimens the surface is thoroughly enamelled by this drying pro- 
cess, and it is an indispensable condition to the complete preser- 
vation of these remarkable fossils. The contour of the foot in 
this species is surpassingly elegant.* In the nomenclature of Prof. 
Hitchcock it is denominated Ornithichnites tuberosus, but it is 
proper to remark that it is not identical with that so named in his 
final report to the legislature of Massachusetts. ‘The tuberous 
expansion of the joints being truly developed in this variety, it 
has received the appellation to which it is eminently entitled. 
This superb variety may be taken as the type of these impres- 
sions, and in its essential elements it is faithfully represented by 
the foot-prints of most species of extinct birds. The identity is 
displayed in the order of the joints, as every example in the col- 
lection will show, the inner toe having two, the middle three, 
and the outer four lobed swellings. This distinguishing feature, 
as far as it goes, is conclusive evidence of this identity, but the 
analogy extends to the claws, which are so distinctly stamped 
that their peculiar form and insertion can be closely traced. In 
most of the specimens this appendage is beautifully illustrated 
and so delicately executed as to suggest the idea that its plantar 
surface was membranous. The analogy is still further main- 
* Most of our réaders have seen the accurate and expressive representatives of 
these forms in the drawings published by Prof. Hitchcock in this Journal, and his 
final State Report, and also those copied from them by Dr. Buckland in his Bridge- 
water Treatise ; otherwish we should illustrate the present paper by several 
drawings.—Eps. 
