THE FROG AND VERTEBRATES IN GENERAL 161 



to the Eutheria, justifies our further consideration of their classi- 

 fication. Considerable variation in the subdivisions of the Eu- 

 theria is found among the various systematists. For the present 

 brief consideration, we may recognize nine orders which we shall 

 arrange as follows : 



Order 1. Insectivora. This order includes certain common 

 species, such, for example, as the Mole, Hedgehog, and Shrew. 

 Gymnura is an important genus. They are small, furry, terres- 

 trial forms, with plantigrade, unguiculate appendages which are 

 variously modified. They are largely insect eaters. (W. fs. 201, 

 205.) 



Order 2. Edentata. Examples of this class are noted in the 

 Armadillo, Ant-eater, and Sloth. Of these, the Armadillo is found 

 in the United States, and it only in Southern Texas. Practically the 

 only characters in common are the absence of the front teeth and 

 the lack of enamel. (W. fs. 89, 204.) 



Order 3. Chiroptera. The Bats, which constitute this order, 

 are characterized by a modification of the fore limbs which adapt 

 them for flight. The hind limbs are clawed and suited for grasp- 

 ing. (W. fs. 207, 227.) 



Order 4. Rodentia. This is the largest order of Mammals in 

 the number of species included. Also the number of individuals 

 of certain species and the extent of their geographical distribution 

 is extraordinary, as, for example, the House-mouse and the Gray- 

 rat. The Rodents are characterized as the gnawing Mammals. 

 They possess one or two pairs of long incisor teeth particularly 

 adapted for this purpose. Their destructiveness together with the 

 disease-carrying ability of certain species make them pests of the 

 first order. All things considered, the Rat is probably the great- 

 est animal pest with which we have to contend. Claws are present 

 on the digits. Additional examples of Rodents are to be found in 

 the Squirrel, Rabbit, Guinea Pig, Beaver, Gopher, Porcupine, 

 etc. (W. fs. 108, 187.) 



Order 5. Carnivora. Although the Carnivores are character- 

 ized as the flesh-eating Mammals and possess certain teeth, par- 

 ticularly the canines and premolars, which are adapted for tear- 

 ing animal tissues, as well as heavily clawed digits, nevertheless 

 species are known which subsist on both animal and vegetable 

 food (omnivorous) or even on vegetable food alone (herbivorous). 

 On the whole, they are fairly large animals with a heavy coat of 



