■2-24l bulletin of the 



are the 5. castanonolus and S. limitis from the little known region of North- 

 ern Mexico and the adjoining Territories northward, whose somewhat 

 doubtful character is particularly mentioned. 



Dr. Gray, in his "Synopsis of American Squirrels," * quotes Professor 

 Baird's remarks respecting the wide variation in color presented by indi- 

 viduals of the same litter, the geographical variation in size, the variations 

 in the hairiness of the soles of the feet at different seasons and between 

 northern and southern representatives of the same species at the same sea- 

 son, and also in respect to the absence or presence of the ear-tufts in dif- 

 ferent individuals of the same species from the same locality ; and so far 

 as he has- followed Baird's memoir his paper is to be commended. As soon, 

 however, as extralimital species are encountered he seems to have lost sight 

 of all these important facts quoted by him, and takes every considerable 

 variation in color as the basis of a species. Hence the greater part of those 

 described by previous authors receive his approval, and some ten or twelve, 

 apparently, are added as new ! The whole number of American Sciuri 

 is thus increased to thirty-nine species. That some of the Mexican species 

 are as variable as those of the United States is beyond question, while it is 

 probable that some of the still more southern ones also are. According to 

 Dr. Gray, the number of species of Asiatic Sciuri is forty-nine, an improb- 

 ably large number, from which the excess can only be properly eliminated 

 by a careful observer residing where these animals live, and the elabora- 

 tion of a mass of material far greater than has thus far been brought to- 

 gether. 



54. Pteromys volucella Desm. Flying Squirrel. Common, 

 but, from its nocturnal habits, not often seen. 



Apparently equally mature individuals from the same locality are quite 

 variable in size, and somewhat in other characters. One, remarkably 

 large, collected by Mr. S. Jillson at Hudson (Mass.), corresponds very well 

 with the P. hudsonius Fischer (P. sabrinus Rich.), which supposed species 

 is almost unquestionably but the large northern race of P. volucella. 



Richardson described, in the "Fauna Boreali-Americana,"f a variety of 

 his /'. sabrinus from the Rocky Mountains, to which he gave the name 

 alpinns (/'. snl>., var. alpinus). Wagner, in his Supplement to Schroeber's 

 Saugethiere, J and Audubon and Bachman in their North American Quad- 

 rupeds, § afterwards raised it to the rank of a species, but apparently with 

 insufficient reason. Professor Baird also admits P. alpinus as a species in 



* Ann. and Mag. Nat. Hist., 1867, p. 415. J Vol. III. p. 230. 



t Vol. I, p. 195, pi. 18. § Vol. III. p. 206. 



