Note 84 — OBSERVATIONS ON THE MINERALOGY AND GEOLOGY OF A PART OF THE UNITED STATES WEST OF THE MISSISSIPPI.

The valley of Red river abounds in limestone, often presenting the shells of oysters and other molluscous animals in a state of petrifaction, scattered in profusion over the surface of the ground, and retaining their original form entire, while on the Arkansa, the rocks are generally sandstone, no limestone being found, except of the Illinois, Grand, and Canadian rivers. Major Long's MS. Journal. Several organic relics from the country about the confluence of the Kiamesha, have been obligingly communicated by Mr. Nuttall: among these is a shell which approaches nearest to the variety of the gryphœa dilatata of Sowerby, 149. fig. 2, but the lobe is far less distinct, and the shell is more narrowed towards the hinge, and is somewhat less dilated, and much more like an ostrea. It may be thus described: G. corrugata, Say.—Small valve, flat, and very much wrinkled, and like the other, narrowed near the hinge. The beak is short, and curved upwards, and laterally, and the sulcus is very distinct. Length, and greatest breadth of the small valve nearly equal; from 1½ to 2 inches. It is in a very perfect state of preservation. Mr. Nuttall brought also from Red river, a species of ostrea, which to the eye appears hardly changed. The anterior portion of the specimens are wanting, but the greatest breadth of the remaining portion of the largest one is nearly three inches. The hinge fosse in this species is proportionably much more contracted, and smaller in every respect, than any other species of the genus we have seen; that of the specimen above mentioned is less than one-half of an inch. The specimens were evidently those of old shells, being much thickened. Another species of ostrea, a hinge fragment of an old and thickened individual, which appears to have been long, and narrow; the hinge fosse itself is long and wide. Length of the hinge more than three inches, greatest width more than one inch.—James.