INTRODUCTION 



Measurements 



Measurements are habitually made in millimeters by mam- 

 malogists because of the widespread acceptance of the metric 

 system in the fields of science. These measurements have 

 been converted to inches in the field book, since most of the 

 readers are accustomed to think in terms of inches. The basis 

 of conversion from millimeters to inches is twenty-five ; that is, 

 twenty-five millimeters equal one inch (this is approximate, 

 but so nearly exact that it serves our purpose) . The measure- 

 ments of mammals usually taken are total length, length of 

 tail vertebrae, and length of hind foot. 



The total length is the distance in a straight line from the 

 tip of the nose to the tip of the tail, not including the hair on 

 the end of the tail. This length is taken by a steel tape or 

 ruler along the back of the mammal, with the body in a 

 straight line, head, neck, and tail extended to give the exact 

 length. 



The length of the tail vertebras is taken from the dorsal root 

 of the tail to the fleshy tip of the tail, the hair on the end of the 

 tail not being included. A common method of securing this 

 dimension is to extend the tail upward at right angles from 

 the back and measure from the rump, at the base of the tail, 

 to the last bit of skin on the tail, the tail vertebrae to be kept 

 perfectly straight. This measurement may also be taken by 

 dividers which are applied to the specimen and then laid on a 

 tape. 



The length of the hind foot is taken from the edge of the heel 

 to the tip of the longest claw, the foot extended and kept fiat 

 so that the curvature of the toes is straightened out. 



These three measurements usually afford a very good index 

 to the size of the mammal. Another useful measurement in 

 some species is the height of the ear, measured either from the 

 crown of the head or from the notch in the lowest part of the 

 basal external margin. The method of taking the ear measure- 

 ment is always stated "from crown" or "from notch." The 

 length of head and body is often important and, of course, can 

 be obtained from the basic measurements always taken, by 

 subtracting the length of the tail vertebras from the total 

 length. 



Weights of mammals are important. This data has not 



