1883.] OF THE ORDERS AND FAMILIES OF MAMMALIA. 183 



tology seems to show, with the Carnivora on the one hand and the 

 Ungulata on the other. In the ' Encyclopaedia ' they were placed 

 at the bottom of the diphyodouts, 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 Ghiroptera 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 

 the absence of hind limbs, are specially adapted to aquatic life. 

 The Rodentia, though generally presenting a low grade of develop- 

 ment, 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 (accord- 

 ing 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 the Marmosets (Hapale) 

 to Man. Certain breaks in the series, however, enable us to divide 

 it into five distinct families : — Hapalidce or Marmosets ; Cehidce or 

 American Monkeys, with three premolar teeth on each side of each 

 jaw; Cercopithecidce, containing the majority of Old-world Mon- 

 keys ; Simiidce, 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. 



Ornithorhynchidse. 

 Echidnidae. 



Proc. Zool. Soc— 1883, No. XIII. 13 



