Allen.] 276 [February 4, 



(Amur Reise, n, 141, tab. ix, fig. 16), and the antennae are also 

 similar in having the intermediate joints elongated. The fifth ven- 

 tral is more strongly emarginate than in the cf of the other two 

 species. The following table will serve to distinguish the three 

 species known to me : 



A. Appendage of claws broad, rounded at tip : — 

 Outer joints of antennse gradually broader, not elongated. 



1. lepturides. 

 Four outer joints slightly wider, joints longer, especially the inter- 

 mediate ones. 2. tenuicorne. 



B. Appendage of claws slender, curved, acute : — 



Antennse very long and slender, nearly filiform. 3. ungulare. 



February 4, 1874. 



Vice-President, Mr. R. C. Greenleaf, in the chair. Forty-four 

 persons present. 



The following paper was read : — 



On Geographical Variation in Color among North Amer- 

 ican Squirrels; with a list of the Species and Varie- 

 ties of the American Sciurid^e occurring north of 

 Mexico. By J. A. Allen. 



Some months since 1 1 had the pleasure of calling the attention of 

 the Society to the subject of geographical variation in size, propor- 

 tions and color among North American birds, and of illustrating the 

 subject by an exhibition of specimens. At the same time I also re- 

 ferred incidentally to variations of a similar character among North 

 American mammals. As remarked on these occasions, the law of ge- 

 ographical variation in size with locality (representatives of the same 

 species decreasing in size with the altitude and latitude of the local- 

 ity) was satisfactorily established by Prof. Baird in 1857 and 1858, 



1 At the meetings of April 17 and June 19, 1872. 



