xiv INTRODUCTION. 
species, although their tendencies must be allowed considerable weight in the balance. 
Taking the Central-American Mammal-fauna as a whole, I think it may fairly be said 
that, of the 177 * known constituent species, at least 100 are essentially Neotropical in 
their character or have Neotropical affinities, while of the remainder not above 60 can 
be said to be decidedly Nearctic. In the carefully drawn-up list of the Neotropical 
genera of Mammals which follows, it will be at once manifest that the Neotropical 
element vastly preponderates in Central America. I have therefore no doubt that the 
Central-American isthmus, at any rate as far north as the isthmus of Tehuantepec, should 
be assigned to the Neotropical Region, of which it should be deemed to constitute a 
distinct province, characterized (1) by the incursion of a considerable number of Nearctic 
forms, especially in the northern districts, (2) by the presence of a certain number of 
peculiar species of Neotropical genera, and (3) as being the focus of the families 
Procyonide and Geomyide, two well-marked groups of Mammals which have extended 
themselves alike into the Nearctic and Neotropical Regions. 
Taste VIII.—Distribution of Neotropical Genera of Mammals. 
Fs dj 3 ; 
= 8 é e g itd S. a 
am | O< 5 < wB FO Ay < 
I. QUADRUMANA. 
I. Crsrpz. 
1. Mycetes ...............0084. 1| .. * * * * 
2, Lagothrix .........0. 0.00 ee 2 * 
3. Ateles....... bene teen ee eens 3 * * * * 
4. Cebls ........ eee eee eee 4 * * * * 
5. Nyctipithecus ................ 5 * * * * 
6. Pithecla .................00. 6 a - - * 
7. Callithrix ...............0.. 7/ .. - * * * 
8. Chrysothrix ................ 8} .. * * * 
II. Hapatipz. 
9. Hapale ...............0005. 9 * * * 
10. Midas ...................0.4. 10 * * * * 
II. CHIROPTERA. 
I. VEsPERTILIONIDA. 
1. Vesperugo ...............00. 11 * * * * * * * 
2, Atalapha.................05. 12 * * * * * * * 
3. Vespertilio ..............005. 13 * * * * * * * 
4. Natalus ...........0...0..004. 14 * * . * 
5. Thyroptera ...............04. 15 - * 
* 7v, e. excluding the introduced Mures. 
