3. _A Poa_, much of the habitat of _Poa sudetica_. Vivid green; leaves plane, rather large; spikelets four-flowered, oval; lower glume one, and the upper three nerved; lower palea distinctly three-nerved, scabrous on the Red nerve. The nerves of the glumes, as well as of the lower palea, are of a vivid green color, and exceedingly prominent. The whole aspect of the plant sent, would rather suggest that it is not indigenous to that section of the country. REGULAR MEETING, SEPTEMBER 4TH, 1865. Mr. Minns in the Chair. Eight members present. Donations to the Library: A paper on the origin and formation of Prairies, by Leo Lesquereux; Report of the Vancouver Island Exploration, 1864; Review of American Birds, by Prof. S. F. Baird; Silliman’s Journal for July; Proceedings of the Essex Institute, January, February and March, 1865; Illustrated Catalogue of the Museum of Comparative Zoology of Cambridge; The Naturalists’ Directory, Part I. Dr. Ayres presented the following paper from Prof. W. P. Blake: Note on the abundance of Iron Ore in Northern Arizona. BY WM. P. BLAKE. In 1863 I observed an iron formation of considerable extent and interest upon and near the William’s Fork of the Colorado, near its mouth. The ore is chiefly the micaceous variety of Hematite, or “specular iron,” and occurs in thick beds and in thin sheets, in a ferruginous limestone or dolomite, evidently metamorphic, and tilted up at a high angle. It forms a belt of peculiar appearance, that may be traced by the eye for miles across the country, in a direction a few degrees south of west. This rock and iron ore is inter-stratified with chloritic and talcose slates and granite, and the series also bears copper ores and gold. From the collections made by Lieut. Whipple’s party, in 1853, in the mountains north, it would appear, that similar rocks exist in the Cerbat and Aquarius Mountains, the extreme geological antiquity of which, was commented on by me in the Pacific R. R. Reports, Vol. III, p. 59. It is possible that this ferriferous formation is connected with the extensive iron formation of the coast of Mexico, south of Acapulco, described by Mr. Manross, (Am. Journ. Sci., XXXIX, 358,) and it may be of pre-Silurian date. Descriptions of New Marine Shells from the Coast of California. PART III. BY PHILIP P. CARPENTER, B. A., PH. D., OF WARRINGTON, ENG. Genus CORBULA, Lam. (Auct.) _Corbula luteola_, Cpr. n. s. State Collection, No. 587.