Original Definition and Fauna of the Group.—Messrs. Gabb and Whitney described two groups of lower Cretaceous beds in California, the relations of which to one another they left doubtful. One of them is extensively represented in the Coast ranges of California, and is especially characterized by the presence of Aucella accompanied by a few other shells, which, as it happens, throws little light on the true horizon. The age suspected was Neocomian. The other set of beds occurs on Cottonwood creek, near Horse-town, in Shasta county. These do not contain Aucella, but carry Ammonites batesii, A. traskii and a considerable number of other fossils, which led Gabb to suggest that they belonged to the Gault. It was evidently his opinion that they were younger than the Aucella-bearing beds, but the two sets were provisionally classed together as the Shasta group.* Professor Jules Marcou recognized only the . . .