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Show 1904. J RODENT DINOMYS BRANICK1I. 159 scientific event that has occurred during the first decennium of the existence of the Para Museum, after the refinding of the long-lost Dipnoan Lepidosiren paradoxa, as fully described in former volumes of the Zoological Society's publications. My surprise was unbounded when, a few weeks ago, I received from a friend of the Museum, personally unknown to me, a cage containing a pair of live large Rodents entirely new to me, notwithstanding a twenty years' acquaintance with the Brazilian fauna, both from the South and the North. These, after a quarter of an hour of eager consultation of the more modern manuals of mammalogy, I recognised as being identical with the almost legendary Dinomys branickii, of which science had lost sight for thirty years. It seems to me to be a most opportune occasion to publish a short description of the external features and the habits of Dinomys, as it is probable that the memoir of Prof. Peters, the only source of information on the subject up to the present, is deficient in these particulars. A series of photographs of the animal, taken in different attitudes spontaneously assumed, supplement my verbal explanations. Doubtless the first impression from the general appearance, especially as regards size and external features, would ally the animal closely with the South-American " Paca " (Agouti paca) ; and the verdict of the scientist as to its systematic location has no reason to differ from the popular conception which has given to our Rodent the local name of " Paca-rana," a, Tupy-term meaning " pseudo-paca." In size the older and larger specimen, the mother, is almost exactly of the dimensions of an average Paca ; the young one is approximately half or two-thirds of that size. The similarity is increased by its capacious head, and the brownish colour marked with distinctly visible longitudinal rows of white spots. This similarity, however, begins to diminish as soon as one undertakes a more minute examination. It presents first the striking difference of having a hairy tail of about 2 decimetres in length. Still further, as regards the hair, while that of the P&ca is soft to the touch and of even length, resembling somewhat the fur of the Otter, Dinomys has a rougher coat of stiffer hairs, uneven in length (these stiffer hairs being white-tipped and longer, and contributing to interrupt the uniformity of the general colour), and forming a first transition-step towards the quills of the coats of the Spiny Rats proper (Loncheriche, Echinomyidse). The white spots are located only on the rear part of the trunk, beginning from the shoulders. They are separated in two groups: (1) four longitudinal rows, nearly continuous at the fore part, the median line of the back being dark; (2) two lateral areas of more or less circular white spots occupying the flanks and thighs, scattered irregularly, as it would seem at first sight, but betraying a tendency to longitudinal arrangement on closer observation. The form of the head of Dinomys may be described as sub- |