Shell small, rather gibbous, transversely subovate. Beaks prominent, incurved, approximate, located about one-third the length of the shell from the anterior end. Anterior outline descending obliquely from the beaks nearly to the ventral margin, where it turns rather abruptly backward along the nearly straight basal edge to the posterior extremity, where it rounds off regularly upward and then forward to meet the hinge. The hinge is apparently straight and more than half as long as the shell. The umbonal ridge is prominent, rounded, ill-defined, fading away at the extremity of the shell. Above this ridge is a depression which, with the smooth, elevated hinge, would cause a strong keel on the shell back of the beaks. The concentric ribs are prominent, fading out at the upper part of the umbonal ridge and near the anterior border. These ribs are quite as prominent on the casts as on the shell itself. On the central and postero-central regions are the characteristic distant, radiating rows of fine, closely set granules. The shell is less convex below and back of the beak than on either side of this region, though it is not concave. The length varies from 1.7 to 1.4 the height. Position and locality: Upper Coal Measures, Howard limestone, Topeka, Kan. This species is very closely related to _A. curta_ Swallow, but differs from it in having a straighter hinge and a more remote beak. It is from a lower horizon. In the latter respect it differs from McChesney’s species also. PALEONTOLOGICAL LABORATORY, INDIANA UNIVERSITY, MAY 22, 1902. Explanation of Plate V. All figures about natural size. Drawings by C. McK. Beede. _Ceriocrinus harshbargeri._ FIG. 1. Right posterior view of type. FIG. 1_a_. Diagram of anal plates of same. FIG. 1_b_. Surface detail enlarged. FIG. 1_c_. Diagram of basal view. FIG. 2. Calyx of another specimen, probably of this species. FIG. 2_a_. Diagram of a portion of posterior view of another slightly smaller specimen, showing variation in size of anal plate. _Aviculopecten subequivalvus._ FIG. 3. View of type. One side incomplete. FIG. 3_a_. Opposite valve of another specimen. _Pinna lata._ FIG. 4. View of type, a left valve. _Pleurophorus whitei._ FIG. 5. Type specimen; cast of a left valve on the same slab as the two following and the cephalothorax of a large limuloid. FIG. 5_a_. Cast off a broken specimen, showing the anterior muscular impressions. FIG. 5_b_. Specimen of different outline. _Allorisma kansasensis._ FIG. 6. Imperfect cast, showing strong concentric undulations impressed upon it. FIG. 6_a_. Lateral view of type. Shell exfoliated in front. [Illustration: PLATE V.]