332 



Measurements of eighteen skulls of LUTRA CANADENSIS. 



MEPHITIS MEPHITICA. 



The twenty-nine skulls of this species of which measurements are 

 given below show a wide range of variation in size, and a decided de- 

 crease southward. The localities embrace such distant points as Cali- 

 fornia and the Atlantic seaboard on the one hand, and Maine and Texas 

 on the other; but, with one or two exceptions, the specimens from any 

 single locality are unsatisfactorily few. The specimens range in length 

 from 2.60 to 3.50, and in width from 1.60 to 2.25 ! Yet there is not a 

 specimen included in the series that is not so old as to have all the cra- 

 nial sutures obliterated. A portion of the difference is doubtless sex- 

 ual, but the specimens, unfortunately, have not the sex indicated. Ten 

 of the specimens may be considered as western, coming mainly from 

 Utah and California ; ten others are from Maine and Massachusetts, 

 and one from Northeastern New York ; three are from Pennsylvania ; 

 and of the remaining five, four are from Texas, and one from Louisiana. 

 The western series of ten average 3.10 in length and 1.95 in width, 

 ranging in length from 2.85 to 3.50 and in width from 1.70 to 2.25. The 

 New England series of ten average 2.88 in length and 1.72 in width, 

 ranging in length from 2.70 to 3.25 and in width from 1.53 to 1.85. The 

 single New York specimen scarcely varies from the average of the New 

 England series, while the Pennsylvania specimens fall a little below. 

 The five southern specimens average 2.73 in length, or a little below the 

 New England series, ranging in length from 2.60 to 290.* 



It thus appears that the western specimens are decidedly the largest 

 of all, and that the northern are somewhat larger than the southern, the 

 specimens compared being of corresponding ages, though of unknown 

 sex, but doubtless comparable in this respect also. 



The difference in size amounts to above one-fourth the size of the 

 largest specimen and above one-third the size of the smallest. Between 

 the western and southern series, the average difference amounts to one- 

 third of the average size of the larger series ! The western series includes 

 the so-called Mephitis occidentalis of Baird, based on California speci- 

 mens, and whose chief difference is merely that of larger size ; yet the 

 four specimens from Ogden, Utah (Coll. Mus. Comp. Zool.), considerably 



* The range in width is not fairly indicated, owing to two of the smaller specimens 

 being imperfect. 



