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Show APPENDIX E.- PALEONTOLOGY. 411 PRODUCTXTS OOSTATXJS? PLATS III. Fio. 2. Reference, De Koninck, Recherches BUT lea Animaux Fossils, premiere partie, page 92, pi. VIIL, fig. 8. The specimen figured is apparently a young individual of this species, in a bad state of preservation. The species is also cited by De K., from the Missouri River, from whence the specimen figured was obtained. Some other fragments from the Platte River appear to belong to the same species. PRODUCTUS SEMIRETICULATUS. PLATE i n . FIG. 8, 5 a and 6 b. Reference, De Koninck, Recherches BUT lea Animaux Fossils, premiere partie, page 88, pL VIIL, IX., and X. I refer, with some hesitation, the specimens here figured, to this yery variable species. One or two of the specimens are very narrow and much elongated; the striae are flexuous, sometimes preserving the bases of numerous spines, and at other times entirely free from these appendages. Other specimens are proportionally shorter and broader, and present the usual form of this species, though none of them are larger than those figured. The specimens are all in limestone of a dark gray or brownish-gray colour, from near Fort Laramie. Some impressions of the same or a similar species occur in limestone from Flat- rock Point, and other places in the neighbourhood of the Great Salt Lake. PRODUCTUS ( sp. indet.) PLATE III. Fio. 4. This species bears considerable resemblance to P. costatus, in the aspect and marking of its surface, but its form is quite different. It occurs on the Missouri River, near Weston, associated with Ferebratulse and other species of Productus, Spirifer, & c. A species of Productus resembling P . punctatus in the character of its surface, occurs on the Big Blue River, in soft shaly limestone; but the specimens are too imperfect for determination. The occurrence of this and other species, shows the existence of carboniferous strata at several points after leaving the Missouri River, and, in some instances, after crossing tracts of country that are probably of cretaceous beds. |