OD aA a Be ee a la OS enim Dean ARE ets 
Geology. 423 
serrate edge. It is about the size and approaches the form of Prof. 
Owen’s figure of Labyrinthodon, Plate 63 A. f. 2, of his Odontographia, 
but it is more flattened. 
Mr. Lea also stated that in the greenish and blackish shales of the 
same locality he found two species of Posidonia, which genus is so char- 
acteristic of this portion of the formation and existing in immense quan- 
tities, As they seem to differ from that figured by Sir Charles Lyell, in 
his Elementary Geology, as coming from the Oolitic coal shale of Rich- 
mond, Virginia, Mr. Lea proposed the names of P. ovata and P. parva, 
the first being about seven-twentieths of an inch in transverse diameter. 
The latter is more rotund, and about three-twentieths of an inch in trans- 
verse diameter, both being covered with numerous minute concentric cost 
over the whole disc. 
Near to this locality and superimposed, Mr. Lea obtained a specimen 
of impure dull red limestone, which contained, on a partially decomposed 
Surface, impressions | ting the apy f Foot-marks, somewhat like 
Chelichnus Duncani, Owen, figured by Sir Wm. Jardine in his Ichnology, 
for which Mr. Lea proposed the provisional name of Chelichnus Wyman- 
ianus, after Professor Wyman, of Cambridge, Mass. : : 
rom the same formation and locality were procured the impressions 
lants, some of which belong to the Conifere. One of the cones was 
h wide. 
Permian) than any other which had comé under Mr. Lea’s notice. _ 
ri 
which the fossils described in the following paper were obtained, occupies 
aN extensive area of country near the head waters of the Missouri, chiefly 
between the 46th and 49th parallels of north latitude, and the 100th, 
and 108th degree of longitude west from Greenwich. According to the 
barometrical measurements made by the party charged with the explora- 
tion of the pro northern route of the Pacific railroad, this district 
varies in its elevation from 1800 to 2700 feet above the present flow of 
the tidal waye,* 
* Some points not crossed by these explorers may be a few hundred feet higher. 
River ; . . F, N, al Le J . 4 
Sei, Philad viii, 101.) —That portion of the’ great Tertiary basin from 
