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Show 1883.] OF T H E O R D E R S A N D FAMILIES O F MAMMALIA. 183 tology seems to show, with the Carnivora on the one hand and Ungulata on the other. In the ' Encyclopaedia' they were placed at the bottom of the diphyodonts, between the Cetacea and the Ungulates ; but this had the disadvantage of widely separating these probably allied groups, and of removing the Insectivora entirely from the Carnivora, with which they form a somewhat natural sequence. The Chiroptera have always been placed near the Insectivora ; but they are really a highly specialized group, as much isolated from all other Mammals by the modification of their anterior limbs in adaptation to aerial locomotion, as the Cetacea and the Sirenia, by tbe absence of hind limbs, are specially adapted to aquatic life. The Rodentia, though generally presenting a low grade of development, are also a specialized group. The position here assigned to them would accord with apparent relationships with the Ungulates, through the Elephant on the one hand, and the extinct Mesotherium on the other. In the present state of the fauna of the earth, the Carnivora form a very distinct order, though naturally subdivided into two groups, the members of the one being more typical, while the other (the Pinnipedia) are aberrant, having the whole of their organization specially modified for living habitually in the water. Lastly, the Primates, which in any natural system must be placed at the head of the series, are divisible into two very distinct groups-one containing the various forms of Lemurs (Lemuroidea), and the other containing the Monkeys and Man (Anthropoidea). Whether the Lemuroidea should form part of the Primates (according to the traditional view), or a distinct order altogether removed from it, is as yet an undetermined question, for both sides of which there is much to be said. There can, however, be no doubt that the Anthropoidea form a perfectly natural group, presenting a series of tolerably regular gradations from tbe Marmosets (Hapale) to Man. Certain breaks in the series, however, enable us to divide it into five distinct families :-Hapalida or Marmosets ; Cebida or American Monkeys, with three premolar teeth on each side of each jaw; Cercopithecida, containing the majority of Old-world Monkeys; Simiida, consisting of the genera Hylobates, Simia, Gorilla, and Troglodytes, the true Man-like Apes ; and, lastly, Hominidce, containing the genus Homo alone. ORDERS, SUBORDERS, AND FAMILIES OF EXISTING MAMMALS. Subclass PROTOTHERIA or Ornithodelphia. Order MONOTREMATA. Ornithorhynchidae. Echidnidae. PROC. ZOOL. Soc-1883, No. XIII. 13 |
