280 THE NORTH AMERICAN GRASSLAND 



producing a mosaic of fragments of the two communities. The dom- 

 inants of this coastal marsh are Spartina spartinae, S. patens, and 

 Sporobolus virginicus. 



Influents. The bison occurred in goodly numbers throughout the 

 prairie area, but the antelope was present only along the northern and 

 western margins. The wolf was represented by the Texas wolf {Canis 

 rujus, A. & B.) and the Texas coyote took the place of the northern 

 species. The Gulf spotted skunk lives in the clusters of Opuntia 

 scattered over the prairie. It is probable that the badger was present 

 in this region, but as a fur-bearer it would be extirpated early. A 

 species of pocket gopher {Geomys breviceps sagittalis Mer.) is re- 

 stricted to this region, and also one of white-footed mice (Baiomys 

 taylori subater Bailey) . The little gray harvest mouse and the Louisi- 

 ana vole are present. The Attwater prairie chicken, the Texas horned 

 lark, and the boat-tailed grackle are characteristic birds (Bailey, 

 1905). 



Tall-grass Orthoptera such as Melanoplus differentialis, Ophulella 

 pelidna, and Sciidderia texensis are common. Amblycorypha huasteca 

 reaches north into the true prairie as far as Kansas. (Cf. Isely, 1937.) 



Serai Stages. The serai stages of this prairie are the gulf bayous, 

 mud flats, and sand areas. The Texas mole (Scalopiis aquaticus 

 texanus Allen) is a sand-area species. In the marshes the rice rat 

 {Oryzomys palustris texensis Allen), the swamp wood rat {Neotoma 

 floridana rubida Bangs) , and the swamp rabbit {Sylvilagus aquaticus 

 littoralis Nelson) are the chief mammals. 



DESERT PLAINS 



Nature and Extent. The term applied to this association refers to 

 the relation between these elevated short-grass plains and the true 

 desert. They lie in contact with the latter on the west and south and 

 partake of the same climatic nature to such an extent as often to have 

 been mistaken for climax desert, an assumption further supported by 

 the large number of succulents and other xeric shrubs (Fig. 65) . 



This association occupies western Texas south of the Panhandle 

 and stretches through large portions of northern Mexico to western 

 Sonora. It is found throughout southern New Mexico and Arizona 

 below elevations of 4,500-5,000 feet, reaching its western limit near 

 the isohyet of 5 inches and approximately 100 miles east of the Colo- 

 rado River. It lies in contact with the coastal prairie, or better, forms 

 a wide ecotone with it in west-central Texas and meets the mixed 

 prairie near the southern line of the Panhandle. Its limits and con- 



