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 the)' 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 cosUe 

 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 presenting the appearance of 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. 



From the same formation and locality were procured the impressions 

 of plants, some of which belong to the Coniferce. One of the cones was 

 nearly six inches long and full an inch wide. These were accompanied 

 by other plants of very obscure character, covering large portions of the 

 surface of some of the layers. Mr. Lea also mentioned that he had ob- 

 served the same Red, Black and Gray Shales at Gwynedd, on the North 

 Pennsylvania Railroad, where he found the same Posidonice, and some of 

 the same obscure plants, impressions of which covered the surfaces of 

 many of the rocks. A single specimen was obtained of a plant with long 

 leaves somewhat resembling Noeggerathia cuneifolia, Brongniart, which is 

 from the Permian. 



In the Black Posidonia Shales was found a single Ganoid scale, which 

 is more like Pygopteris mandibular is , Agas., from the Marl Slate (Lower 

 Permian) than any other which had come under Mr. Lea's notice. There 

 were other obscure forms observed, which have not yet been satisfactorily 

 found to be analogous to any known forms, but which Mr. Lea hoped to 

 be able to make out when he should figure all the specimens and describe 

 them more at large for the Journal of the Academy. 



10. Descriptions of New Species of Acephala and Gasteropoda, from 

 the Tertiary formations of Nebraska Territory, with some general re- 

 marks on the Geology of the country about the sources of the Missouri 

 River ; by F. B. Meek and F. V. Hayden, M. D., (Proc. Acad. Nat. 

 Sci., Philad., viii, 101.) — That portion of the great Tertiary basin from 

 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 proposed northern route of the Pacific railroad, this district 

 varies in its elevation from 1800 to 2700 feet above the present flow of 

 the tidal wave.* 



* Some points not crossed by these explorers may be a few hundred feet higher. 



