THE FAMILY OF MICE AND RATS 219 



4. Learn some of the distinguishing characters of each 

 example. 



5. Study the comparative sizes of the various types. 



6. Finally, in determining the name of a strange species, 

 do not feel that you must name it instantly or be disgraced! 

 Take time to think over it, and to "look it up." Snap judg- 

 ments on small creatures have a most annoying habit of prov- 

 ing to be wrong. It is a wise judge who knows when to 

 hand down a decision. 



In order to make the genera of North American rats and 

 mice clear to the student, I have procured from Dr. C. Hart 

 Merriam, the highest living authority on these creatures, a 

 fine, perfect, adult specimen of the best-known (or most 

 typical) species of each genus. Figures of these skins are 

 here reproduced to show their relative sizes, and a life-like 

 illustration of each of these types is also given. In the text, 

 the most striking distinguishing characters are printed in 

 italics. 



With these aids to the text, it should be possible for a 

 clear-headed, keen-eyed student to refer any adult North 

 American rat or mouse to its proper genus. But beware of 

 young specimens! Often they are so puzzling that Solomon 

 himself could not place them with any degree of certainty. 

 In determining the species of mice and rats, mammalogists 

 depend largely upon the characters of the teeth; but that is 

 a subject too intricate for the general student. 



The table on page 222 shows the various Families of rats 

 and mice, the North American genera, and the typical spe- 

 cies of each. It is not necessary for young students to mem- 



