MEXICAN TAILLESS AMPHIBIANS 111 



converging rows behind and within level of choanae. In case of two 

 other cotypes, having head-and-body lengths of 38 and 41.7 mm., 

 respectively, the tibio-tarsal joint reaches to between eye and tip 

 of snout when the hind limb is carried forward along the body. 



It is apparent from the synonymy of E. mexicanus that some of 

 the more pronounced variants of this species have been incorrectly 

 allocated generically. Some of the confusion that has prevailed in 

 the past may possibly be explained by the occurrence of occasional 

 individuals that lack vomerine teeth. Of the 13 specimens of this 

 frog in the National Museum, all from the State of Oaxaca, there are 

 two with a white vertebral stripe at least 1 mm. wide, one with a 

 white pin stripe, and the remainder show no trace of a vertebral line. 

 Most of them have a short dermal ridge above the edge of the scapula. 

 Eight have more or less distinct converging dorsal dermal folds, 

 while five show no trace of such folds. On some the skin of the 

 upperparts is roughened by dermal ridges, and on others it is quite 

 smooth. The skin on the posterior half of the abdomen is generally 

 areolate, but occasionally is smooth. No trace of vomerine teeth 

 can be observed in 3 of these specimens, and in the remaining 

 10 these teeth vary not only in the width of the series, but also in the 

 extent to which they project beyond the gum. 



In general E. mexicanus has a much more variegated appearance 

 than E. rhodopis. Darker colors predominate, and the black and 

 brown mottling of the upperparts is especially noticeable. The dark 

 bars on the hind limbs are quite distinct. The tarsal fold is normally 

 absent, though this distinction will not hold invariably. 



Certain specimens from the west coast of Mexico are rather puz- 

 zling, for they approach rhodopis in some details and mexicanus in 

 others. They are tentatively assigned to this species until a larger 

 series is available to determine their precise relationships. A short- 

 legged individual (U.S.N.M. No. 47433) collected by Nelson and 

 Goldman at Plomosas in Sinaloa is referred to E. mexicanus partly on 

 geographical grounds and partly because of the absence of a tarsal 

 fold, although in general appearance it bears some resemblance to 

 E. rhodopis. When the hind limb is carried forward along the body, 

 the tibio-tarsal joint barely reaches the anterior margin of the eye. 

 This dull-colored individual has a dark interorbital streak behind 

 the light-colored snout, and a pair of short black glandular ridges on 

 the mid-dorsum. Distinctive markings on the side of the head 

 consisting of subvertical dark brown bars, separated by narrower 

 light spaces, that extend across lower and upper lips to eye and loreal 

 region are also present. 



Three specimens (U.S.N.M. Nos. 47905-07) were found about 

 springs and little streams in dense growths of grass and other plants 

 at 10,000 feet altitude at Cerro San Felipe. One (U.S.N.M. No. 



