The plate-like form of the ossiculæ, and their mode of articulation with each other, by an extension horizontally inwards, as we have described above, in the case of those plates which we have considered as the _second costals_, seem to indicate, that this species ought to be referred to the second division of the crinoidea, or _semiarticulata_ of Miller. It certainly, however, cannot be at all referred to poteriocrinites, the only genus which that author has framed in this division of the family. We refrain from distinguishing it by a name either generic or specific, until other specimens can be obtained, in which the characters are less equivocal. We have two _second costal plates_, which made part of distinct individuals, larger than the above described one. Of these the surface of one is perfectly glabrous, whilst that of the other has light orbicular indentations instead of tubercles; a third very small one is perfectly smooth like the first, and doubtless formed part of the body of a young individual. Another plate found near the same spot with the above, is of a somewhat triangular form exteriorly, or rather like the face of a truncated pyramid, of which the middle of the summit is a little produced in the form of a right angle, thus offering a scollop on each side of the apex for the adaptation of superior ossiculæ. On divesting it carefully of its extraneous matrix, we discovered that it was readily adjusted by its base to the summit of those segments of the fragment above described, which we have supposed to be _second costals_, a prominent line on its base corresponding with the inner one of those grooves which we have described, to characterize the superior face of those plates. This plate, then, agreeably to the relations in which we have viewed the preceding pieces, must be a _scapula_; it is susceptible of considerable hinge-like motion, and appears to have been much less firmly attached to the costals than the latter are to each other. 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.