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Show 376 In the July number of the American Journal of Science for this year ( 1876), voL xii. page 81, Mr. G. B. Grinnell; of New Haven, has described a very interesting new genus and species of Crinoidea, from the Cretaceous rocks of the West. This fossil was first discovered by Professor Marsh, some years back, in Utah, and has since been found in Kansas. Professor Mudge had also sent specimens of it to me last winter from Kansas, and I had in course of preparation the accompanying cuts, with the view of illustrating and describing it; but on learning from Professor Marsh that Mr. Orinnell was about to describe it, my name and description were withheld from publication. Mr. Grinnell kindly sent me, soon after, a copy of his description and figures in advance of the issue of the Journal of Science in which they are published: and on examining these, I find that our specimens show some parts of its structure more clearly than those studied by him. Consequently, it seems desirable that our cuts, with some additional remarks on this curious Grinoid ( the only known American Cretaceous type of the order), should be published. Like those investigated by Mr. Grinnell, none of our specimens are in a condition to show the base of the body; but from its general physiognomy as presented in our specimens, and more especially from the entire absence among the numerous associated fragments, of any disks of columns, I think Mr. Grinnell very probably right in supposing that it may have had no column, or, in other words, may have been free. As nearly as can be determined from the specimens yet known, the body of the type- species seems to have presented a slightly depressed- subglobose form, and is composed of nearly flat, or scarcely convex, thin plates, joined together by slightly- channeled sutures, and without cost ® , nodes, or other distinct markings. In some instances, these body- plates present the appearance of being a little beveled along their ed^ es, and irregularly subimbricating; but this appearance may be deceptive. As already stated, we know nothing of its base, or of its subradial pieces, if it possessed the latter. If it was a free Crinoid, and at all related to Marsu-pitesy it will probably be found, like that genus, to have a central piece, surrounded by basals, alternating with subradials, the latter also alternating with and supporting the radial series. It may, however, be as widely distinct from Marmpites in the structure of the basal parts of its body as in those above. Our specimen, represented by theforegoingcut, Fig. B, shows twoof the rays, with their divisions, one of the interradial fields with parts of two others, andtwo of theinteraxillary spaces. Bach of the two rays thusseen, at least as far down as they can be traced, has three primary radial pieces, the lowest on e in each ray being wider than long and more or less nearly hexagonal in outline; while the second is narrower and hexagonal or pentagonal, the third again larger and hexagonal, and bears on each of its superior sloping sides, in direct succession, two large secondary radials. On the second of the latter, a kind of false bifurcation takes place: that is, there is given off here on the interradial side, a large arm- lik$ series of pieces, the second of which is largest, while the others above diminish rapidly in size upward. This arm- like series, however, does not form a proper arm, or become free at all, excepting perhaps at its attenuated upper extremity, but connects laterally over the interradial field . with the corresponding series from the next ray, so as completely to isolate the interradial pieces, and to unite with each other and with the divisions of the rays on each side, to form a part of the walls of the body. Going back to the second of the secondary radiate from which each of the lower arm- like series mentioned above is given off/ we find that the main division of each ray is continued almost directly onward from |
