PROBLEMS OF DISTRIBUTION AND THEIR SOLUTION. 157 



and 120 genera at least being confined to the waters of the 

 area. 



Central America, as might be expected, shows less clearly the 

 characteristic features of the southern portion of the continent. 

 There we find a commingling ofNearctic with Neotropical forms, but 

 the latter predominate, and as far north as Mexico we may trace the 

 howling monkeys and armadillos of the southern region. 



In the case of the West Indian Islands, forming \h&Antillean sub- 

 region of the Neotropical province, however, we meet with greater 

 variations from the fauna of the continent. No better instance of 

 the apparently arbitrary, but nevertheless logical and scientific, 

 method of mapping off the earth's surface for biological purposes, 

 could well be selected, than the zoologist's classification of the West 

 Indian Islands. For, encircling Cuba, Hayti, Jamaica, Porto Rico, St. 

 Vincent, Barbadoes, and many other islets in his biological line, he 

 places outside this line Tobago, Trinidad, Margarita, and Curagoa. 

 The elimination of these latter islands from the "zoological" West 

 Indies, whilst they form characteristic islands of the geographical 

 Antilles, is readily explicable. Trinidad and its three neighbouring 

 islands in their zoology differ entirely from the other West Indian 

 Islands, but agree with the adjoining coast of South America in the 

 character of their included animals and plants. Scientifically and 

 zoologically, they are therefore parts of South America ; they belong 

 to the Brazilian sub-region, and not to the West Indian sub-province. 

 Their affinity to the continent in the matter of their botany and 

 zoology, and their wide divergence from the other West Indian 

 Islands, point clearly to their relatively late detachment from the 

 South American coasts. Their constitution as islands was attained, 

 in other words, at a date much more recent than that at which the 

 other islands of the group received their status as independent 

 lands. Of Trinidad and its neighbouring islets nothing peculiar in 

 a zoological sense can be detailed. We may, therefore, turn to the 

 typical West Indies themselves. 



Rich in vegetation and all that contributes to the support of 

 animal life, the West Indies are poor in representatives of the higher 

 groups. But they compensate the zoological mind for poverty in 

 numbers by peculiarities of type. No apes or carnivora are native to 

 the West Indies, and the characteristic edentates of South America 

 the sloths, ant-eaters, and armadillos are likewise wholly absent. 

 But bats are abundant, and the rodents are peculiar. Capromys, one 

 of these rodents, inhabits Cuba, Jamaica; and Plagiodontia is found 

 in Hayti alone. These two genera are thus exclusively limited to- 

 the West Indies. In addition, an agouti is found in St. Vincent, and 

 other islands ; and a rare species of mouse (Hesperomys) is found in 

 Hayti and Martinique. If the West Indian rodents are peculiar, 



