93 
* The specimen now exhibited was one of those described by 
Col. Foster. It is half of a lower jaw, nine inches in length, 
having the general form of the corresponding bone in the 
living beaver, but more than twice as long. The most strik- 
ing peculiarities of this specimen, apart from its size, are the 
strong striation of the exterior surface of the great incisor, 
and the figure formed by the enamel-folds of the molars. 
These are distinctive of the genus. 
This specimen was found at Nashport, on the Ohio Canal, 
in a bed of peat, which was buried under strata of clay and 
sand, and apparently belonged to the same age with the 
Forest bed found in the middle portion of the drift deposits 
of Ohio. The teeth of Castoroides have also been met with 
in a similar peat-bed in Montgomery County, Ohio. The 
Rochester specimen was taken from a deposit of peat lying 
behind one of the old beaches which mark the ancient shore 
lines of Lake Ontario, when the water stood at a higher level 
than now. 
In Europe, the remains of an extinct beaver have likewise 
been found in Post Tertiary deposits; and this has been 
called Trogonthertum Cuvier. It was intermediate in size 
between Castoroides and Castor,and the teeth and bones show 
differences from both, and such as have been considered of 
generic value. 
Pror. J. J. STEVENSON presented an account of the 
Lignites of Colorado, as observed and studied by him—with 
particular reference to the question of their age—during 
the summer of 1878, while accompanying the expedition of 
Lieut. Wheeler. 
The age of the lignites of Colorado is still disputed; but 
the evidence, both stratigraphical and paleeontological, seems 
to show altogether that they belong to the later Cretaceous. 
At Cation City we find the Lower Cretaceous, consisting of 
massive sandstones with some dark shales. Above these are 
the shales and limestones of the Middle Cretaceous, contain- 
ing the characteristic fossils of that period. These pass imper- 
ceptibly through a mass of clay into a loose-grained reddish 
sandstone containing impressions of Halymenites major, Lesqx., 
and very indistinct impressions of mollusca, This sandstone 
includes thin beds of lhegnite, and is regarded by Hayden and 
Lesquereux as Kocene. On it rests the lignite series proper, 
containing many fragments of leaves, but no marine fossil 
other than the fucoid already referred to. The whole series, 
