290 PRINCIPLES OF ANIMAL BIOLOGY 



taxonomic position as the genus. Thus the ranges of the species of the 

 American genus Scaphiopus, the spade-foot toads, are given in a recent 

 check-list as follows: Scaphiopus couchii, Texas to Arizona, northern 

 states of Mexico, Lower California; Scaphiopus hammondii, western and 

 southwestern states from Montana to Texas and Mexico, and west- 

 ward to the Pacific states; Scaphiopus holbrookii holbrookii, eastern states, 

 Massachusetts to Florida, west to Louisiana, Texas to Arkansas; Scaphio- 

 pus holhrookii albus, Florida Keys and possibly the extreme southern part 

 of the peninsula of Florida; Scaphiopus hurterii, Texas. 



Differences in Size of Range. — Just as there are great differences in 

 the geographical position, so there are wide differences in the size of the 

 range occupied by different forms. The ranges of the larger taxonomic 

 groups (families, genera) are of course more extensive than those of their 

 subdivisions (species, varieties), when they have more than one division, 

 because of the wide differences in the position of the ranges of the lesser 

 groups. Thus, the range of Gopherus polypheynus, one of the gopher 

 turtles, is the coast of the United States from southern South Carolina to 

 Florida and the Mississippi River and north into southern Arkansas; 

 the range of Gopherus agassizii is in the deserts of southwestern Arizona, 

 southern Nevada and southeastern California; and Gopherus herlandieri 

 occurs in the southwestern corner of Texas and northeastern Mexico. 

 Therefore the genus Gopherus which includes these three species has 

 a range extending, with interruptions, from the Atlantic to the Pacific. 

 Furthermore, the family Testudinidse, which includes the genus Gopherus 

 and a number of other genera, is cosmopolitan in the temperate and trop- 

 ical regions except Australia and Papuasia. 



There are, moreover, very great differences in the extent of the ranges 

 of groups of the same rank, and great differences in the physical condi- 

 tions inhabited by dilferent forms. It has been stated above that the 

 family Testudinidse is cosmopolitan except in Australia and Papuasia. 

 In contrast to this extensive range the family Carettochelydidae (also 

 turtles) is confined to the island of New Guinea, and the family Dermate- 

 mydidse to Central America. The genus Camponotus (the carpenter 

 ants) is found everywhere in North America (also on other continents) 

 from the tops of the highest mountains to the lowest desert basin, from 

 the Atlantic to the Pacific, and from the tundras of the north polar region 

 to the tropical region along the gulf; while another genus of ants, Sym- 

 pheidole, has been found only in the Garden of the Gods in Colorado. 



Differences in the size of range of species may be illustrated by some 

 of the North American species of the genus Hyla (the tree frogs). Hyla 

 versicolor is found from southern Canada to the gulf states and from the 

 Atlantic coast to Minnesota, Iowa, Arkansas and central Texas; Hyla 

 squirella from Virginia to Florida, west to Texas, and northward up the 



