SCIURID^— SCIUROPTERUS VOLUCELLA. 057 



Alaska and Louisiana, Nova Scotia and California, and from many interme- 

 diate localities. As shown by the subjoined table of measurements, there is 

 a gradual decrease in size from the north southward. The average length 

 of specimens (exclusive of the tail) from Arctic America is about 7.50; of 

 specimens from near the 49th parallel, about 6.85, or a little less, ranging 

 from 7.10 to 6.50; of specimens from Northern New England, about 5.75, 

 ranging from 6.00 to 5.35; of specimens from Southern New England, about 

 5.25,* ranging from 5.50 (or even 6.00) to 4.50; of specimens from the Gulf 

 States, about 4.75, ranging from 5 20 to 4.30, or about one-third less than 

 the most northern specimens. 



In respect to color, specimens from the same locality sometimes differ 

 in the color of the dorsal surface as much as do the most diverse examples 

 from widely separated localities. There are, however, easily recognized local 

 differences of coloration, especially in respect to the tail; but even here there 

 is a considerable individual (or seasonal?) variation. As a rule, the speci- 

 mens from north of the United States have darker tails than those from south 

 of the parallel of 44°, while the average difference in color between northern 

 and southern specimens is quite marked. 



A series of five specimens from the Red River of the North nearly 

 covers the whole range of variation in color exhibited by the whole series 

 No. 3257 (Red River Settlement) is dark fuscous-brown above, with the tail, 

 especially the distal half, decidedly blackish, and the under parts faintly 

 washed with rusty-fulvous. No. 3717 (same locality, December 10) is soft 

 yellowish-brown above, with the tail much less dusky, and the under parts 

 white, with merely the faintest tinge of yellow. No. 3718 (same locality 

 and date) is quite similar, but shows a variation toward No. 3257. No. 1153!) 

 (Pembina, June 14) is much redder than 3717; the tail is especially brighter, 

 with much less dusky. No. 9083 (Selkirk Settlement) is very light-colored 

 (as light as any from any locality), being pale yellowish-brown above, with 

 only the terminal third of the tail blackish. 



'Many of the New England specimens (mostly measured from alcoholic specimens) are evidently 

 immature. In the case of the males, the testes are generally abdominal, and the females show no sign 

 of having suckled young. All the males with the testes scrotal and all the females with the teats bearing 

 evidence of maternity are of much larger size than the others. All the measurements of northern speci- 

 mens have necessarily been taken from skins, some of which are evidently overstuffed. Taking, how- 

 ever, only such measurements as are least affected by faulty taxidermy, as the length of the feet and the 

 measurements of the head, in cases where the skull is left iu the skin (and only from such specimens are 

 the measurements of the head given), there is evidently a very striking, as well as very gradual, decreaso 

 in size southward. 



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