A segment of a crinoid animal, which seemed to have been a first costal joint of a pentacrinus of Parkinson, occurred near the same place.
22. Productus pectinoides, Say.—Convex valve, with a central longitudinal indentation; the whole surface is longitudinally ribbed, each rib being marked by two striæ, in addition to the central carina.
The shell is not of frequent occurrence, and a perfect specimen has not yet been obtained, but the portions we have examined, are sufficient to show that it is perfectly distinct from either of the species we have mentioned. We do not find any species figured or described by authors like it.
23. Productus compressus, Say.—Shell much compressed, with numerous acute striæ, upwards of fifty in number on each valve, the alternate ones rather smaller; a very slight central longitudinal indentation on the convex valve; outline suborbicular; hinge edge rectilinear, shorter than the greatest breadth of the shell.
Greatest breadth from 3⁄5 to 1 inch. In its proportions it resembles the truncated portion of the productus of Martin, as represented on his plate 22. fig. 3. It is very common.
24. A shell of the length and breadth of three inches sometimes occurs, the convex valve of which is transversely undulated, its umbo prominent, and curved like that of a gryphæa, its tip resting on the base of the opposite valve which is concave, with a transverse linear base; its muscular impressions seem to have been lateral.
25. A single specimen was found of a valve of a shell, in some degree resembling a pecten, but without the auricles. Length more than 23⁄10 inches.
26. Productus lineolatus, Say.—Valves with numerous, fine, equal, equidistant, longitudinal striæ, and a few small tubercles; convex valve very much elongated, its basal portion is curved downwards, almost perpendicularly with respect to the disk near the umbones.
So singular is the structure of this shell, that the internal cavity appears to have been perfectly transverse, with respect to the general length of the shell, and small in comparison with the length. It strongly resembles the anomites productus of Martin, as represented on plate 22. fig. 102. of his Petrif. Derbi., and like that shell it is armed with small tubercles, though fewer in number, and the striæ are much more numerous and smaller.
27. Cast of a turretted univalve, probably a cerithium, of the length of 2½ inches.