THE BATKACHIA OF NORTH AMERICA. 307 



Tbis species has the Qiost nortberu rauge of those found west of the 

 Mississippi, and is especially characteristic of the elevated plains. It 

 ranges from northern Texas to Montana. It resembles very closely 

 half grown specimens of Bufo cognatus of the same region, so as to con- 

 stitute it a mimetic analogue. 



1^ #;^ 5^ ^^ 



Fig. 78. Spea hammondii bombifrons Cope. 9943, nat. size. Camp Thome, Yellowstone K. 



Measurements of No. 3520. 



M. 



Length of head and body 043 



Length of head, including tympana 012 



Width of head, iuclnding tympana 016 



Length of fore-lea; from axilla 020 



Length of hind leg from groin 0445 



Length of tarsus 007 



Length of tibia 014 



Length of rest of foot 017 



The specimen 9943, from the Yellowstone Kiver, is an excellent illus- 

 tration of the mode of origin of corneous epidermis. The end of the 

 muzzle and the frontal convexity are covered with a layer of black 

 born, each forming an oval shield, which meets the other on the top of 

 the snout. This is probably a result of the constant pressure and fric- 

 tion of the earth when the animal is burrowing in it. Although the 

 animal burrows with the hinder limbs, the muzzle is naturally used in 

 keeping the passage-way open to the surface. The character is not con- 

 stant. 



This species is characteristic of the northern parts of the i)lains and 

 Great Basin. I found it especially common in the region north of the 

 Missouri River and eastward of Fort Benton. Before my arrival there 

 rain had fallen, and the ruts of the wagon-trails were filled with water. 

 These ditches contained numerous examples of this species, together 

 with Ghoro;pMUis triseriatus, Bufo cognatus, and AmhJystoma tigrinum. 

 Their metamorphosis was completed by that time (August 20), although 

 some of the specimens were small. 



In Idaho, near latitude 43° 30', is situated a body of water known as 

 Market Lake. Its extent is variable, for it is said to be dependent for 

 its water supply on the overflows of the Snake Eiver, which is a few 

 miles distant to the eastward. An old channel leads from the river to 

 the lake, giving probability to the statement. At the time of my pas- 

 sage through the region the water was unusually high, for a portion of 

 the stage road, with parts of numerous telegraph j^oles, was submerged. 

 The lake appeared to be about ten miles long by six in width. The 

 country surrounding it is arid, and the sand, which represents soil, rests 



