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Show 1871.] DR. J. E. GRAY ON THE BRADYPODIDA. 431 of skulls. In five of them (7366, young, 736a, 607, 910, and 736d) they are separated from each other by a space of considerable width. This space is much narrower behind in 1510c-, which is a much older skull than any of the others. In three skulls (1510a, 1510) from Costa Rica, both of which are young, the temporal muscles are only separated by a very narrow ridge for about half or three-quarters of an inch; in an adult skull, that wants its hinder part (1510), they appear to approximate much further forward, but the occipital part of the skull is deficient. The malar bones are very different in shape in the different specimens : in some the descending bone is very broad and fan-like, and in others it is comparatively small; the ascending one varies much in length, but is generally short, not reaching the zygomatic process and squamosal; but in one specimen from Costa Rica it nearly reaches the process, to which it is united by a cartilage. There is a great difference in size, shape, and vesicularity of the pterygoids, and also in the substance, some being very thin and others thick and hard. 1. CHOLCEPUS. 1. CHOLCEPUS DIDACTYLUS, Gray, P. Z. S. 1849, p. 65; Catalogue, p. 363; Wagn. Suppl. vol. iv. p. 158. One, which is generally dark, has the end of the hairs of the occipital crest white, and more or less tinted with bright green. A young specimen received from Mr. Salvin is covered with short woolly hair, of a dark brown colour, rather paler on the rump, much paler on the head, the cheeks and chin, the band across the nose, and the orbits being dark brown. All these specimens have pale, whitish claws, while the claws of the other species are of a dark brown or blackish colour. Dr. Peters says the C. didactylus has long and C. hoffmanni short claws, but I cannot see any difference in the length of the claws in the Museum specimens of the two species. The claws are short in the young specimens, and become longer as they increase in age. There is an adult specimen in the British Museum, presented by Captain Kellett, of H.M.S. 'Herald,' without any special habitat, which agrees with Mr. Salvin's specimens in having very long hair and white claws, but is of a nearly uniform dark brown colour, rather paler on the head, and redder beneath. The hair of the middle of the back and of the cervical crest has more or less long white tips ; and these tips of the hairs of the cervical crest have a decided green tint. The specimens of this genus appear to be very variable in colour and in length of hair. A specimen said to have come from Juan de Fuca, received from the Haslar Hospital, has short hair of nearly uniform length, and is of a uniform dark brown colour, with scarcely any indication of an occipital crest. Two specimens from Brazil are like the former; but the hairs are longer, and the colour is rather paler, and there is a more decided nuchal crest. |