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Show 612 PROF. w. H. FLOWER ON [Dec. 6, 3. On the Pygmy Hippopotamus of Liberia, Hippopotamus liberiensis (Morton) \ and its claims to distinct Generic Rank. By W . H. FLOWER, C.B., LL.D., F.E.S. [Received November 15, 1887.] The Zoological Department of the British Museum has lately acquired a complete skeleton and skin of a fully adult P y g m y Hippopotamus. This animal has been separated generically from Hippopotamus by Leidy 2, under the name of Chceropsis; and Leidy's view has been adopted by Alphonse Milne-Edwards3 (who has given a very careful description of the whole skeleton), by Gratiolet4, and by others5. The two points of generic distinction insisted on are : - I. The absence of the outer pair of lower incisors which are found in Hippopotamus amphibius. II. The very different proportions and relations of the parts of the cranium. It is admitted that in all other structural characters the two forms are closely allied. I. With reference to the dentition, we may recall the division which was made long ago by Dr. Falconer6 of all the then known species of Hippopotamus living and extinct into two subgenera, Hexa-protodon and Tetraprotodon, according as they had three or two incisors on each side of the jaw. The former term was afterwards raised to generic rank by Owen7 , the old generic name Hippopotamus being retained for Tetraprotodon. Accepting this distinction as a valid one, it was logical on the part of Leidy, on the discovery of a form with only one incisor in the lower jaw, to separate it also generically. In his revision of the group, M r . Lydekker does not accept these divisions as generic, remarking that " the case of H. palaindicus, which in its lower jaw is really a Hexaprotodon in process of conversion into a Tetraprotodon, coupled with the instance of unilateral hexaprotodontism in H. amphibius, indicates that Dr. Falconer's two subgenera should be abolished. This point being admitted, there are but slight grounds for retaining the subgenus or genus Chceropsis, 1 Hippopotamus minor, Morton, Proc. Acad. Nat. Sciences Philadelphia, 1844, p. 14. Name withdrawn, as preoccupied, in favour of H liberiensis, Morton, Journ. Acad. Nat. Sc. Philad.2nd ser. vol i. p. 232 (1849). 2 Chcerodes (Proc. Acad. Nat. Sc. Phil. vi. p. 52), withdrawn, as preoccupied, in favour of Chxropsis (Journal Acad. Nat. Sc. Philad. 2nd ser. ii. p. 213, 1853). 8 Reeherches pour servir a l'histoire naturelle des Mammiferes : Paris, 1868, p. 77. 4 Reeherches sur l'Anatomie de l'Hippopotame: Paris 1867. Apparently unaware of Leidy's generic name, Gratiolet proposed that of Bitomeodon (p. 202). 5 Macalister, " The Anatomy of Chxropsis liberiensis," Proc. R. Irish Academy, 2nd ser. i. p. 494 (1873). The existing literature of this interesting species is completed by reference to a description and figure of the sternum (which was absent in the skeleton described by Milne-Edwards) by Peters, Monatsbericht Ak. Berlin, 1873, p. 445. 8 Falconer and Cautley, Asiatic Researches, xix. pt. i. p. 51 (1836). 7 Odontography, p. 566 (1840-45). |