xiii PHYLUM CHORDATA 581 



Zealand regions, and in South America, but occur in all the other 

 provinces. 



The Chiroptera are world-wide in distribution, occurring in 

 greatest abundance in tropical and warm temperate zones. The 

 Flying Foxes (Pteropidse) are absent from the Nearctic and Neo- 

 tropical regions, and the Vampire Bats occur exclusively in the 

 latter. 



The distribution of the Lemurs is remarkable ; they occur only 

 in Madagascar, a limited part of South Africa, Southern India and 

 Ceylon, some of the islands of the Malay Archipelago, and the 

 Philippines. The headquarters of the group is the island of 

 Madagascar, of which they constitute one half of the entire 

 Mammalian fauna. 



Of the other groups of Primates, the Marmosets (Hapalidae) and 

 the Cebidae are exclusively American ; the Cercopithecidae Palso- 

 arctic, Oriental and Ethiopian, with a single species in Madagascar. 

 Of the Simiidas the Gibbons occur only in South-Eastern Asia and 

 the Malay Peninsula ; the Orangs only in Borneo and Sumatra ; 

 the Gorilla and Chimpanzee in certain parts of Western Equatorial 

 Africa. 



Geological Distribution. - - The earliest fossil remains of 

 Mammals have been found in strata of Upper Triassic and of 

 Jurassic age in Europe and America. These remains consist 

 almost exclusively of jaws and teeth, and, as the latter differ 

 widely from those of existing Mammals, there is frequently great 

 difficulty, in the absence of remains of the other hard parts, in 

 determining the affinities of these Mesozoic forms. Some of the 

 Triassic and Jurassic Mammalian molar teeth are constructed on 

 the most primitive form of the triconodont type, which has already 

 been referred to (p. 544) as being the primitive form in the class, 

 having three cones or cusps in a longitudinal row. In Dromatherium 

 and its allies each molar has a single main cusp with two smaller 

 accessory cusps. There is no decisive evidence as to the affinities 

 of these primitive triconodont Mammals, but they may be pro- 

 visionally set down as allied to the Prototheria. 



Of the remainder of the Mesozoic Mammals, some were probably 

 Prototheria, others Metatheria, while others again may have been 

 Insectivores. Most of them fall into two main groups. The type 

 of dentition presented by the members of one of these groups 

 (Fig. 1239) is more nearly allied to that of the Polyprotodont 

 Marsupials (p. 464) than to any other. In the other group (Multi- 

 tuberculata) (Fig. 1240) there is a superficial resemblance to the 

 Diprotodont Marsupials ; a single chisel-shaped incisor is present on 

 each side of the lower jaw, and one large, and sometimes one or 

 two smaller, on each side of the upper. A wide diastema separates 

 these from the pre-molars. The molars present a number of variously 

 arranged small tubercles. In some cases the pre-molars have a 



