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Show 1008 DR. J. E. GRAY ON THE RHINOCEROTIDAE. [Dec. 12, to have belonged to a male. The size and form of the cavity is, no doubt, greatly influenced by the age of the animal. The masseter muscle becomes thicker and shorter as the animal increases in age, the transverse width of the skull under the muscles becoming less as the animal becomes more aged (see some measurements, showing the fact, under R. javanicus). The same is shown to be the case in the series of skulls of R. unicornis. Mr. Edward Blyth has published a memoir on the living Asiatic species of Rhinoceros, with figures of some of the skulls in the M u seum of the Society, which may be consulted with advantage (see Journal of the Asiatic Society of Bengal, xxxi. 1862, p. 151) ; but unfortunately I have not had the power of comparing the skulls with those in the London collections :- Rhinoceros indicus: narrow type of skull, t. 1. f. 1, t. 2. f. 1. jR. sondaicus: broad type of skull, t. 1. f. 2, t. 2. f. 2, from the Bengal Sundarbans, and Tenasserim ; t. 1. f. 3, t. 2. f. 3, aged, from Java. R. sumatranus, t. 3. f. 1, 2, male; t. 3. f. 3, female. R. sumatranus, Tavoy, t. 4. f. 1-4. The figures are from photographs, and they show the form of the occiput in the three species, confirming the fact that the occiput of the two-horned species is always flat and erect. 1. RHINOCEROS. Skin divided into distinct shields by deep folds. Lumbar fold well marked, and extending from the groin to the back. Horn one, short, conical. Upper lip with a central prominence. Skull:-forehead broad, flat, or only slightly rounded ; the occipital end shelving from the occipital condyle to the occipital crest; the occipital condyles large, oblong, very prominent; lachrymal bone moderate. The skulls of the larger number of species of this genus have the forehead and the upper surface of the nose flattened; this is seen in the living animal. But one species, of which there is only a single skull of a young animal in the British Museum, has the forehead and nose subcylindrical (that is, high on the central line and arched on the sides), as is the case with the Sumatran and the African Rhinocerotes. This character, I have no doubt, is equally visible in the living animal. A. Forehead and nose behind the horn flat. Nose square on the sides above ; nasal short. R. javanicus. Nose shelving on the sides above ; upper jaw slightly contracted before the grinders. Nasal broad, elongate R. unicornis. Nasal narrow, short R. nasalis. Upper jaw much contracted before the grinders ; nasal narrow, short R. floweri. B. Forehead and nose subcylindrical, shelving on the sides above; nasal elongate ........ R. stenocephalus. |