Pelobatidae 



This Spadefoot is especially characteristic of the elevated 

 plains of the Western part of the continent. It has the habits 

 of the Eastern Spadefoot (Scaphiopus holhrookii), in that it bur- 

 rows during the greater part of the year, only coming out during 

 heavy and continued rains. In its range it is very abundant, 

 and so when it does appear, every ditch and pool of water may 

 show representatives. Being dependent on rain, its breeding 

 season varies greatly from year to year. Cope observed speci- 

 mens in Montana in which the metamorphosis was completed 

 August 2oth. He observed in Idaho the full-grown, fat larvae 

 with the tails unabsorbed trying to feed upon animal food. They 

 were in small burrows that they had made in the wet sand some 

 distance from the lake margin. Some of them, in which the meta- 

 morphosis of the mouth had proceeded so far that there was a 

 wide gape, had whole grasshoppers ' in their mouths or partially 

 projecting from them. This observation also was in August. 



This Spadefoot croaks vigorously when taken in the hand. 

 The throat swells into a resonating pouch wider than long, and 

 widest just back of the jaws, in a line with the front of the arm 

 insertions. The creature is very active and alert in habit. It 

 burrows into sandy soil dexterously and rapidly, using the feet 

 and legs to good effect. The curved horny 'elevations on the 

 head combined with the shortness and thickness of the muzzle, 

 produce a most curious pug-dog expression. The horny arches 

 are probably closely connected with the burrowing habit, the 

 head being used to keep the burrow open in front. The amount 

 and hardness of this horny growth of the epidermis of the head 

 varies in different specimens: there may be a thin dark-coloured 

 layer only, or the horn may be thick and as black and hard as is 

 the inner sole tubercle. In some specimens this black horny sub- 

 stance is found not only on the head but also in a broad dorsal 

 band. 



1 Caloptenus spretus. 



63 



