MEXICAN TAILLESS AMPHIBIANS 19 



1866. Spea Cope, Journ. Acad. Nat. Sci. Philadelphia, new ser., vol. 6, pt. 1, 

 p. 81, July. [Genotype, S[caphiop7is] bombifrons Cope, 1863, Proc. Acad. 

 Nat. Sci. Philadelphia, vol. 15, p. 53, Mar. (type locality not designated, 

 but the cotypes were obtained at Fort Union on the Missouri River, latitude 

 48° N.; on the Platte River, 200 miles west of Fort Kearney; and at Llano 

 Estecado, Tex.).] 



The genus Scaphiopus is the only representative of the family 

 Pelobatidae in North America. The several species breed in 

 temporary pools after rains, and the ropelike egg mass is attached 

 to water weeds. Wright has found that the eggs of Scaphiopus 

 hammondii are occasionally stalked. The egg has two capsules in 

 addition to the vitelline membrane. In one species, *S. holbrookii, 

 the intracapsular development is very short, the larvae hatch in an 

 immature condition, and the frontal gland initiates the hatching 

 process, the tadpoles emerging before the gills are formed. The 

 tadpoles of Scaphiopus have simple teeth. 



KEY TO MEXICAN SPECIES OF SCAPHIOPUS 



1. Glandular enlargements or parotoid glands variable in their 

 presence, generally limited to a thickening of the skin in 

 scapular region; skin of upperparts generally conspicuously 

 warty, covered with closely spaced large tubercles, especially 

 on sides and shoulders; a conspicuous pair of light-colored 

 supra-anal spots; vomerine teeth in two clusters either be- 

 tween or at level of posterior margin of choanae; tympanum 

 visible or concealed by hypertrophy of parotoid; canthus 

 rostralis scarcely indicated; head flat or slightly concave 

 between the eyes; cephalic ossification incomplete; underparts 

 smooth, with a few rounded areolae; fingers in order of 

 decreasing length, 3, 1, 4, 2; palm smooth except for con- 

 spicuous elongated inner metacarpal tubercle and less dis- 

 tinct smaU outer metacarpal tubercle; fingers essentially free, 

 with a vestigial web on each side of second finger rarely 

 present; first and second fingers of breeding males with horny 

 nuptial excrescences; heels not meeting when legs are flexed; 

 web complete or strongly scalloped, in which case the distal 

 phalanx is largely free on all toes but fourth, on which the two 

 distal phalanges either are or are not bordered with dermal 

 fringe; sole smooth except for large external metatarsal 

 tubercle with black cutting edge; toes in order of decreasing 

 length, 4, 3, 5, 2, 1; color pattern of upperparts variable; 

 darker coloration restricted chiefly to V-shaped interorbital 

 band and anastomosing blotches or wavy cross bands in 

 thoracic and sacral regions, which may or may not interrupt 

 distinct or indistinct longitudinal light stripes; generally a 

 pair of blotches of same color in scapular region; longitudinal 

 light-colored stripes when present 2 to 4 in number, the inner 

 pair of which are on a line with inner margins of orbits, and the 

 outer with tympanum; vertical light-colored stripe on tip of 

 nose; fore and hind limbs with transverse dark crossbars; head- 

 and-body length of adults, 55 mm hammondii multiplicatus (p. 22) 



