x INTRODUCTION. 
Upon examining this Table it will be found that the 181 species contained in it fall 
into five different categories, as regards their distribution, namely :— 
I. Nuarcrre Sprcres, 2. e. Central-American species also found north of Mexico ............ 48 
II. Neorropicat SPxEcrEs, 2. ¢. Central-American species also found south of Panama ........ 65 
III. Neoezan Spxcizs, 7. ¢. Central-American species found north of Mexico and also south of 
Panama .. 1. eee ccc cee eee ee ee eee eee ee ee eee tee eee e eee ee eens 17 
IV. AvrocurHonovs Spectres, 7. ¢. species not yet known to occur except in Central America .. 47 
V. Intropucenp Sprcrms (Mures) .... 6. cece eee eens bees pecans nese seus 4 
181 
We will now shortly consider each of these categories separately. 
I. Nearctic SPECIES. 
The species belonging to this section of the Central-American Mammal-fauna have 
been divided by Alston into four categories, which serve to exhibit very clearly the 
gradual diminution of the Nearctic forms as we proceed southwards through Central 
America. These are set out in the subjoined Tables. 
TasEe I1.—Nearctic Species found in the Northern States of Mexico, but not recorded 
from south of 25° N. lat. 
1. Antrozous pallidus. 10. Cariacus macrotis. 
2. Nycticejus crepuscularis. 11. Spermophilus spilosomus. 
3. Atalapha intermedia. 12. Cynomys ludovicianus. 
4. Vespertilio subulatus. 13. Castor fiber. 
5. Taxidea americana. 14. Neotoma floridana. 
6. Ursus horribilis. 15. Thomomys talpoides, 
7. americanus. 16. Perognathus flavus. 
8. Ovis cervina. 17. fasciatus. 
9. Antilocapra americana. - 
Taste III.—Nearctic Species found in Central and South Mexico, but not recorded from 
south of the Isthmus of Tehuantepec. 
1. Vespertilio nitidus. 10. Heperomys aureolus. 
2. Felis rufa. 11. californicus. 
3. Canis lupus. 12. palustris. 
4, Bassaris astuta. 13. Ochetodon humilis. 
5. Sciurus arizonensis. 14, Arvicola pinetorum. 
6. Spermophilus grammurus. 15. Dipodomys phillipsi. 
7. mexicanus. 16. Lepus sylvaticus. 
8. Hesperomys leucopus. . 17. callotis. 
9. aztecus. 18. aquaticus. 
