124 THE NEOG^IC REALM. [CHAP. 



ostriches of the Old World. The hoatzin (Opisthocomus\ the oil- 

 bird (Steatornis\ and the boat-bill (Cancroma) are likewise 

 peculiar Neogaeic types. Still more remarkable is the solitary 

 Andean survival (Ccenolestes] of the diprotodont marsupials of 

 the Santa Cruz epoch. A curious feature of the Neogaean 

 forest-mammals whether they belong to the old fauna or the 

 new is the frequency of prehensile power in the tail. Not only 

 does this occur in several genera of monkeys, but also in Cerco- 

 leptes, Synetheres, Chcetomys, Capromys prehensilis, Cydoturus, 

 Didelphys, and Ccenolestes. A parallel is to be found elsewhere 

 only in Australia. 



After referring to the deficiency of the many types of 

 mammals alluded to in an earlier paragraph of the present 

 chapter, the author adds that "Among birds we have to notice the 

 absence of tits, true flycatchers, shrikes, sun-birds, starlings, larks 

 (except a solitary species in the Andes), rollers, bee-eaters, and 

 pheasants, while warblers are very scarce, and the almost cosmo- 

 politan wagtails are represented by a single species of pipit 



Whether, therefore, we consider its richness in peculiar forms of 

 animal life, its enormous variety of species, its numerous defici- 

 encies as compared with other parts of the world, or the prevalence 

 of a low type of organisation among its higher animals, the 

 Neotropical region stands out as undoubtedly the most remark- 

 able of the great zoological regions of the earth." 



The distinctness is, however, by no means confined to 

 mammals and birds. Of the land molluscs, Mr A. H. Cooke 1 

 writes that they present a marked contrast to those of North 

 America. "Instead of being scanty, they are exceedingly 

 abundant; instead of being small and obscure, they are among 

 the largest in size, most brilliant in colour, and most singular 

 in shape that are known to exist. At the same time they 

 are, as a whole, isolated in type, and exhibit but little relation 

 with the Mollusca of any other region." 



Having arrived at the conclusion that the original Neogseic 

 mammalian fauna, exemplified in the Santa Cruz 



Origin of the 



Santa Cruz beds, has not been derived from North America, 

 it remains to endeavour to account for its origin. 

 1 The Cambridge Natural History Mollusca, p. 342 (1895). 



