202 



VERTEBRATE ZOOLOGY 



sometimes have adhesive pads on the toes. Only one genus need 

 be mentioned. 



The genus Hylodes, of which there are nearly 50 species, is one of 

 the best known. They are tree-toads much like those of the genus 

 Hyla. Hylodes martinicensis is a tiny frog in which the pairing and 

 egg laying take place on land, the eggs in a foamy mass being glued 

 to a leaf. The large eggs, about 4-5 mm. in diameter, develop 



practically to metamorphosis before 

 hatching, the aquatic larval period 

 being omitted (Fig. 117). 



Family 6. Engystomatidce (Narrow- 

 Mouthed Toads). They are some- 

 times called "toothless toads." A 

 representative of this family in the 

 United States is Engystoma caroli- 

 nense, a family common in the old 

 South. They are sharply distin- 

 guished by the dilation of the sacral 

 diapophyses. Perhaps the most sig- 

 nificant feature of the family has to 

 do with their ant-eating habits and 



adaptations for it. It is well known 

 FIG. 117. Hylodes martinicensis. ,1,1 . i * .. . 



1, an egg with embryo about seven that the ant-eating habit in various 

 days old; 2, another, twelve days groups of vertebrates is associated 

 old; 3, the young frog just hatched; w j tn ra ther definite changes in struc- 



, ,-,, , 



ture ' These fr S s have a narrow 

 mouth, protruding snout, toothless 



condition, hidden tympanum, modified feet and shoulder girdle for 

 digging; these are also characters of ant-eaters in other vertebrate 

 classes such as Reptilia and Mammalia. 



Family Ranidce. These are the "true frogs" and, to dwellers of 

 the northern hemisphere, the most familiar of amphibians. Two 

 small families, one consisting of one species, the other of about a 

 dozen species, differ from the Raninse (the typical frogs) chiefly in 

 the teeth. 



Sub-Family 1. Ceratobrachince, with teeth in upper and lower jaws. 

 Ceratobrachus guentheri is a native of the Solomon Islands. 



Sub-Family 2. Dendrobatinoe. Arboreal frogs of small size without 

 any teeth. The toes have adhesive disks. Members of the genus 



all by %; 4, adult male xl. (From 

 Gadow, after Peters.) 



