MEXICAN TAILLESS AMPHIBIANS 91 



1830. Enydrobius Wagler, Natiirliches System der Amphibien, p. 202. [Sub- 

 stitute name for Hylodes Fitzinger, 1826.] 



In this review ten species of the genus Eleutherodadylus are recog- 

 nized within the borders of Mexico. Three of these, mexicanus, 

 rhodopis, and rugidosus, have been taken much more frequently than 

 any of the others. Larger series of dunnii and venustus, obviously 

 related to rhodopis, are necessary for an accurate determination of 

 their status. The robber frog, E. augusti, is quite closely related to 

 E. laticeps. The species laticeps and longipes seem to be the rarest of 

 all Mexican eleutherodactylids, since at present they are known from 

 one and two individuals, respectively. The specimen taken north of 

 Vera Cruz by Duges and referred to E. melanostidus by Giinther in 

 his Biologia Centrali-Americana, 1900, p. 236, is the only reported 

 occurrence of this species in Mexico, and as this determination has 

 been questioned it has not been listed herein. 



In contrast to many other well-known kinds of frogs, some of the 

 species referable to Eleutherodadylus hatch fully formed from the 

 egg capsules. Their larvae have a peculiar hatching mechanism, the 

 so-called egg-tooth, which consists of a horny structure derived from 

 modified epidermis. There are, however, many species of Eleuthero- 

 dadylus whose life histories are entirely unknown. Although direct 

 development is definitely known to take place in a few species, this 

 may not necessarily be the invariable process. The Texan cliff frog, 

 or robber frog, E. latrans, is reported by Strecker to pass through a 

 tadpole stage in the water. 



According to Noble ^° — 



The diagnostic characters of the life history of Eleutherodadylus are the ter- 

 restrial mode of egg-laying, the large eggs with two or more resistent capsules 

 devoid of peduncles or "foam," the absence of tadpole mouth parts, the presence 

 of a premaxillary egg tooth, and a broad highly vasculated tail. 



The life histories of the two species studied by Noble " are suppos- 

 edly typical for most of the members of this genus; the following 

 quotation summarizes the essential steps in their development : 



The eggs of the various species of Eleutherodactylus may be laid between leaves 

 of epiphytes, palms, bananas, etc., or on the ground under rocks, logs, vegetation, 

 or merely in a hole in the bank. The breeding site may be near water or far 

 away from it. As a rule, each species has a definite habitat preference for its 

 eggs, but this is not constant. I have found in Santo Domingo that two species, 

 E. abbotti, and E. flavescens, may lay their eggs among leaves above the ground 

 or on the ground at the base of reeds. Development is in these species direct. 

 All species of Eleutherodactylus fully investigated have been found to have an egg 

 tooth lying directly over the symphysis of the premaxillae. This may vary in 

 size and shape in the different species. I have found that E. abbotti on hatching 



« Noble, G. K., The value of life history data in the study of the evolution of the Amphibia. Ann. Mew 

 York Acad. Sci., vol. 30, p. 90, Oct. 31, 1927. 



" Noble, O. K., The hatching process in Alytes, Eleutherodadvlus, and other amphibians. Amer. Mus. 

 Nov., no. 229, pp. 4, 5, Oct. 14, 1926. 



