36 



BULLETIN 160, UNITED STATES NATIONAL MUSEUM 



Type locality. — Valley of the Gila and Colorado Rivers. 

 Range. — Vicinity of streams with permanent flow of water from 

 Guadalupe Canyon in northeastern Sonora north to Turkey Creek 

 near Prescott in central Arizona, and in the lower Colorado River 

 Valley from Fort Mohave to Fort Yuma; also occurs in Imperial 

 County, Calif. Exact limits of range unknown. Reported from 



Guaymas (Mocquard) and Cajon Bonito 

 Creek (Meams), Sonora. 



Remarks. — This large toad frequents 

 the hottest portion of the North Amer- 

 ican Continent, and, although it has 

 never been found in the strictly desert 

 areas, it seems to be extending its range 

 with the advent of irrigation. It has 

 been described as semiaquatic and, ex- 

 cept in irrigated areas, is seldom ob- 

 served during the dry season. The eggs 

 are laid during the first heavy summer 

 showers in temporary pools of water or 

 in shallow streams. 



Exceptionally large individuals may 

 be rather uncommon, and the maximum 

 size attained by this species can not 

 be ascertained by the limited material 

 available. One specimen (U.S.N.M. 

 No. 66734) measures 160 mm. in head- 

 and-body length. The distinctive char- 

 acters of this species are a smooth 

 leathery skin, large size, and greenish 

 color. Unlike other Mexican toads, it has a large elongate gland on 

 the forearm and several smaller ones on the hind limb. 



Major Mearns,^ in describing his experiences with this large toad, 

 states : 



Of batrachians, a toad (Bufo) and a frog {Rana virescens hrachycephala Cope) 

 were found at Warsaw Mills; and at Buenos Ayres, at the beginning of the sum- 

 mer rains, Lieutenant Gaillard observed great numbers of a very large frog-like 

 toad, named Bufo alvarius by Girard. Nothing was seen or heard of them until 

 the advent of the early summer rains, which formed a large shallow lake near 

 Buenos Ayres and about 10 kilometers (6 miles) north of the Boundary Line. 

 These large toads then filled the air with their loud cries, which increased until 

 a deafening roar was produced. Numbers of them were seen hopping about, but 

 their rarity was not suspected by Lieutenant Gaillard, on which account none 

 were collected. The range of Bufo alvarius Girard, extends from Monument 



Figure 4.— Head of Bufo alp art us 

 (U.S.N.M. No. 21063) from Guadalupe 

 Canj'on, Sonora, Mexico: a, Lateral 

 view; 6, dorsal view 



' Meams, E. A., Mammals of the Mexican boundary of the United States. U. S. Nat. Mus. Bull. 56, 

 pp. 113, 114, 1907. 



