T he subject of the present notice was submitted to me by Henry H. Shirley, Esq.: it was found in Jamaica in a river-course which is composed of red conglomerate and sandstone, overlaid by limestone, differing from the general tertiary carious limestone of the Island and beneath it: the locality is near “Freeman's Hall Estate, between the Parishes of St. Elizabeth and Trelawney, at that central high ground or ridge which forms, as it were, the back-bone of the Island.” (MS. note sent with the specimen.) The fossil was imbedded in a nodule of hard calcareous shelly rock, which had been broken in pieces: three of the largest of these contain portions of a skull, which, on being partially cleared of the matrix, exhibited the following characters:— An occipital portion with two condyles, and a tolerably capacious brain-case, showing its mammalian nature (Pl. XV. fig. 1); and a facial portion, figs. 2 & 3, with the fore part of the lower jaw, fig. 4, indicative of an affinity to the Manatee, but with well-marked characters distinctive from any known existing member of the Order Sirenia. The foramen magnum is subcircular, a little wider across than vertically; measuring 1 inch across. The condyles are 4 lines apart at their lower ends, with the articular surface divided into two triangular facets, meeting at rather more than a right angle, along an oblique ridge, where the surfaces are continuous. In Manatus the occipital foramen is broader across, and the condyles are more uniformly convex