114 MONOGRAPH OF THE GENUS SCIURUS. 



The species existing in Louisiana and in the territories bor- 

 dering on Texas, require a more careful examination, and the 

 vast and varied regions between the Rocky Mountains and 

 the Pacific, and especially those portions bordering on the 

 Mexican possessions, will no doubt present species not yet 

 enumerated. 



Order RODENTIA. 



Genus Sciurus, Linn., Erxleb., Cut., GeofFr., Illiger. 



Eng. Squirrel. Gr. Smugo;. Fr. Ecureuil. Genu. Eichorn. 



Dental formula.— Incis. §. Can. fjg. Grind. |$ or ff.—20 or 22. 



Squirrels are distinguished by large inferior incisors much 

 compressed; by long tails generally longer than the bo- 

 dy, furnished with hairs arranged on the sides so as to re- 

 semble a feather. The tail, when the animal is in a state of 

 rest, is usually turned over the back and head, and partially 

 conceals the body. All true squirrels are destitute of cheek- 

 pouches. They have on the fore feet four toes, with a short 

 rudimental thumb, protected by a blunt nail. On the palm 

 are five tubercles, three of which are situated at the roots of 

 the toes, and two larger ones behind. The third toe from the 

 inner side is longer than the second, which distinguishes the 

 squirrels from the marmots and spermophiles. In the hind 

 foot there are five toes, with four naked callous eminences on 

 the sole at their roots. They have four large grinders on a 

 side in each jaw ; these are variously tuberculated. In young 

 animals there is a small additional grinder above in front, 

 which, in many of the species, very soon drops out, but in 

 the majority of our American squirrels this fifth grinder is ei- 

 ther permanent, or remains for more than a year. The mam- 

 ma are eight in number, two of which are situated on the 

 chest, and six on the sides of the belly. They produce from 

 four to six young. 



The squirrel is admirably adapted to a residence on trees, 

 for which nature has designed it. Its fingers are long, slen- 

 der, and deeply cleft, and its nails very acute and greatly com- 

 pressed. It is enabled to leap from limb to limb, and from 

 tree to tree, clinging to the smallest twigs, and seldom miss- 

 ing its hold. When this happens to be the case, it preserves 

 its instinctive habit of grasping in its descent at the first ob- 

 ject which may present itself; or if about to fall to the earth 

 it spreads itself out in the manner of the flying squirrel, and 

 thereby presenting a greater resistance to the air, is enabled 



