216 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



The measurements of the specimens preserv.ed are as follows: — 



Spermophiltjs franklini, {8ab.) Rich. 



The Gray Gopher is quite common in this vicinity. It is not, however, 

 an exclusively Ground Squirrel, being often seen on trees, and here its 

 hole is usually found in a dead tree, but sometimes is dug at the foot of 

 a tree. I believe it lays in a store of provisions sufiQcient for its winter 

 use, and scarcely ever emerges from its home during this season, for 

 careful search has failed to reveal its presence during winter. 



It breeds about June 25th, and I believe but one litter is brought 

 forth each year. The female suckles her young for five or six weeks. 



Professor Baird, in his work on North American Mammals, pp. 306 

 and 315, is in error in stating that the "head is pure gray, without any 

 tinge of yellowish". Such is undoubtedly thecase with the young; but in 

 mature specimens there is not only a tinge of yellowish, but this colora- 

 tion is quite distinct, and occurs sufficiently often to consider it a normal 

 marking of this mammal. I have observed the yellowish coloration 

 extend as far on the head as the eyes, and also on the upper part of the 

 tail for about one-fourth of its length. 



The cheek-pouches of S. franJclini open internally, directly into the 

 mouth, and are quite small, having a capacity of about one-third of a 

 teaspoonful only. 



The pouches themselves have no true muscular structure, being sim- 

 ply a pocket-shaped duplicature of the skin of the sides of the head, 

 and possessing no more elastic power than this tissue ordinarily does. 



The pouches do not extend quite to the ears, and we observe nothing 

 like the muscular structure of the pouches of Geomys and Ihomomys, 

 which possess a true constrictor and a contractor muscle, but there is de- 

 flected from the posterior portion of the sac a special tendon, broad 

 (comparatively speaking), which replaces the muscle found in the species 

 of Geomys and Thomomys^ but which soon becomes part of, and is lost 

 in, the superficial fascia of the sides of the neck. 



