MURIDJ3— SIGMOUONTE8-H. LBUOOPUS aONORIENSIS. 



83 



We will next show tlxit the shoit-tailedness ot var". sonoriensis likewise 

 characterizos, ulinost uncxceptionally, the mice of Arctic Nortii America. 

 Indeed, this fact has already been shown in the previous table, wliich we intro- 

 duced to settle the mi/oidex question ; these additional specimens, indeed, 

 are merely the rest of our Arctic lot, positively the same as those of the 

 "myoides" table. Most of these Arctic ones are noticeably larger than United 

 States specimens, as was to have been expected ; they average about 3.66 iu 

 lengtii, with tail about 2.75 ; while the relative lengths of tail and body of 

 sonoriensis are nearly repeated, about half an inch has been added to the abso- 

 lute lengths of both trunk and tail. The feet are rather smaller, both abso- 

 lutely and relatively, than in true leucopus, averaging only 0.75, notwithstanding 

 the increase of general size. This feature, as well as the shortness of the tail, 

 might be explained upon the well-known law of smallness of |)eripheral parts 

 in Arctic animals; but it is curious that it should correspond exactly with the 

 shortness of tail of the New Mexican animals, which, of course, are not 

 amenable to this law. The tail and feet are both unusually hairy. Here is 

 the table : — 



-iti 



Table XX.—Me(uureiHeniH of sUty-tiiHC {and tut of other) additional »peoimen» of Brilisk American and Arctic 

 He8I*kkomyh LF.ucorus, nu)9tiy of the **Miiori«n«is" ett/te. 



[Nut much roliiiuce can be placoil on the ilry mcaauremoiita, at the eUna aro all badly prepared, beiog nlmoat withoat 

 exoopttuD overstuffed, tbe talla iM'tng aktnued aud distorted, and Itau feet liaviDg the toes curled up.] 



-I 



