824 THE AMERICAN NA TURALIST. [Vol. XXXVII. 



are principally used for throwing back the loose earth. Although 

 not acquiring the excessive development of the fore limbs, the 

 femur usually has its trochanters well developed. In Erinaceus 

 it has a strong ridge below the third trochanter. Greater 

 strength is given by the partial anchylosis of the tibia and 

 fibula ; in Chrysochloris the}' are welded at the lower end. 

 Strength is effected in the pes by the great development of 

 the calcaneum, which plays a prominent part in pushing the ani- 

 mal forward. In Talpa the pes has a large sesamoid bone at the 

 side of the tibia corresponding to the os falciforme of the manus, 

 but otherwise it exhibits none of the great modifications of the 



C. Physiological Modifications. 



1. Hibernation. — In the temperate zones where the ground 

 is frozen during a portion of each year, fossorial mammals would 

 have difficulty in getting food. Especially is this the case with 

 those semi-fossorial forms such as the woodchuck which live on 

 soft succulent herbage. Such forms are thus compelled to spend 

 the winter in a long sleep (c. woodchucks, gophers, ham- 



Partial List of Fossorial and Semi-fossorial Mammals. 



Monotremata : Ornithorhynchus, Echidna; Marsupialia: Phas- 

 colomys, Dasyurus, kangaroo rat. Ih-ttongia Lscuiri, pig-footed 

 bandicoot (Chocropus castanotis), marsupial mole (Notoryctes 

 typhlops); Edentata: Dasypodidae, Orycteropus ; Insectivora : 

 Talpa, Condylura. Sealops, water shrew {Crossopits fodiens), des- 

 man (Myogale), Erinaceus, Oryzoryetes, Chrysochloris ; Roden- 

 tia : Eepus, Spermophilus, Cynomys, Arctomys, Geomyidae, 

 Spalacidae, Rhizomys, Octodontidre, Ccelogenys, Viscacha 

 {Lagostomus trkhodactylus), Bathyergidae, Heterocephalus ; 

 Carniyora : Lutra, ratel (Mellivora), Javanese skunk (Mydaus), 



cation along fossorial lines evidently include the following : reten- 



