PREFACE. 



them. The extent of the dispersion of each named form has, how- 

 ever, been given so far as our present knowledge permits. 



In the Synopsis and its Supplement 997 species and subspecies 

 were enumerated, and of these 789 were restricted to the regions 

 north of the boundary of Mexico, leaving 208 that were found on 

 both sides of the line. Of genera there were 120 of which only 42 

 were not represented in Mexico. In the present work the species 

 and subspecies number i,oi8,of which 809 are restricted to Mexico 

 and the countries and islands embraced in the volume, leaving 209 

 also to be met with in the United States. The genera number 178, 

 of which 78 are found north of the line, leaving too peculiar to the 

 Southern lands, the major portion of the excess over the northern 

 genera being found in the Chiroptera. The Land Mammals in the 

 Synopsis numbered 933, and the Sea Mammals 63; in the present 

 volume the Land Mammals number 989 and the Sea Mammals 29, 

 and but two of the latter are not found in northern waters so far 

 as known, Megaptera n. bellicosa and Prodelphinus longirostris , 

 although the first named probably does go into the northern portions 

 of the Gulf of Mexico. 



The following table exhibits the genera that are represented on 

 both sides of the northern boundary of Mexico, with their species and 

 subspecies, showing the number of those that are restricted to each 

 region, and also how many are common to both: 



