On the Peculiarities That Distinguish the Manatee of the West Indies from the Dugong of the East Indian Seas

XXVI. On the peculiarities that distinguish the Manatee of the West Indies from the Dugong of the East Indian seas. By Sir Everard Home, Bart. V. P. R. S. Read July 12, 1821. Having received from the Duke of Manchester, Governor of the Island of Jamaica, a manatee preserved in spirit, which is a species of dugong, but very different from that of which an account has so lately been read to the Society, I am desirous to add some observations upon this species, the whole tribe of animals having hitherto been little known with respect to their internal structure. The manatee differs in its external form from the dugong, the tail being much broader, and the ribs having greater lateral extension. As this animal feeds upon the plants that grow at the mouths of great rivers, and the dugong upon those met with in the shallows among small islands in the Eastern Seas, this difference of form will make it more buoyant and better fitted to float in fresh water; while its habits of life place it between the dugong and hippopotamus. There are no tusks. The snout is flattened, and upon the ends of its toes there are nails, as is shown in the annexed drawing, (Pl. XXVI.) The teeth differ in number from those of the dugong, there being twenty-four molares, six on each side of each jaw. The skull has the orbit nearly a compleat circle; the intermaxillary bones are curved at their union, but the length of curvature is only two inches. The bones of the ear resemble those of the dugong. The skeleton in the general view is similar to that of the dugong. The number of vertebrae is forty-eight, seven to the neck, seventeen to the back, twenty-four to the tail, which last have long transverse processes tipped with cartilages. The ribs are thicker and more massy than in the dugong, and considerably more spread out. There are seventeen on each side. The great and little toe have only two phalanges. The toe next the great one has three, the third four, and the fourth toe three phalanges: these are shown in the drawing of the skeleton. The stomach differs from that of the dugong in the solid glandular part being more pyramidal, and connected to the general cavity by a neck, and the two lateral pouches being wider and shorter, the posterior the largest. The food was found to be fuci. The cæcum consists of a large globular bag with two finger-like hollow processes, unlike the cæcum in other animals, and therefore is represented in the annexed drawing. The uterus resembles that of the dugong. The heart and lungs were not in a state to be examined. In these two species of this extraordinary tribe of animals, between which there is so great a resemblance, the teeth are totally different, which shows the mode of classing animals from the appearance of the teeth to be very erroneous. The engravings, Plates XXVI. XXVII. XXVIII. XXIX. require no particular explanation, as the scale is marked on the plates.