14 THE BIOLOGY OF HARDING COUNTY 



(descended from those brought to Mexico and liberated by the 

 Spaniards in the i6th century. For some unknown reason the 

 native American horses became extinct on this continent shortly 

 before the glacial period). There were present large herds of. 

 bison, elk, antelope and many bighorn sheep, bear and puma, and 

 more large birds such as the cranes, grouse, ducks, etc., than there 

 are now. Various small mammals such as some kinds of mice, 

 etc., were doubtless more rare than now, as is also the case with 

 numerous kinds of birds, "weeds" and household insects. 



3. Explanatory Remarks. 



In the treatment of the biology of a diversified area it is 

 desirable to sub-divide the region into sections having many simi- 

 larities. In this area there are native perhaps 50 kinds of mam- 

 mals, 200 kinds of birds, 15 kinds of snakes, lizards and turtles, 

 6 kinds of amphibians, over a thousand species of insects and con- 

 siderably over 500 kinds of plants. In addition there are the 

 fishes, mollusks, crawfish, worms and many smaller forms. Of 

 this vast array of life very many are inconspicuous and not ob- 

 served by non-specialists, although without a doubt every species 

 has its part to play in the biologic economy of the whole. This 

 is made the more likely when it is noted that most of the species 

 have a definite place to occupy. The plants and animals of the 

 ponds are not at all of the same species as those of the hill tops, 

 those of the shaded ravines not at all the same as those of the level 

 prairies. 



It is therefore convenient to sub-divide this area into several 

 biological associations or ecological formations. The largest as- 

 sociation is that of the "Grass-covered Uplard," "Steppe," or "Dry 

 Prairie." Other important formations are (b) the "grassy Flats" 

 along the stream valleys, (c) Woods in the ravines and along 

 the streams, (d) Hne-covered and. Rocky Slopes, (e) Badlands, 

 (f) Sandy areas, (g) Streams, Ponds and Marshes. 



It is noticeable that these several formations are primarily 

 characterized by their topography, secondarily by their vegetation 

 and lastly by the animals which inhabit them. This is in reverse 

 order of the motility and is to be expected. The topography is 

 practically unchangeable except when considered in a geological 

 sense. The individual plants are stationary, but the species is 

 movable by means of the seeds, runners, etc. In the case of the 



