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. Engystomatidoe (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 

 that the ant-eating habit in various 

 groups of vertebrates is associated 

 with rather definite changes in struc- 

 ture. These frogs have a narrow 

 nn)uth, protruding snout, toothless 

 contlition, hidden tympanum, modified feet and shoulder girdle for 

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

 classes such as Reptilia and Manunalia. 



Family Ranidw. — These arc the "true frogs" and, to dwellers of 

 the northern hemisphere, the most familiar of amphiluans. 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. Ceratobrachiuai, with teeth in upper and lower jaws. 

 Ceratobrachus gucntheri is a native of the Solomon Islands. 



Sub-Family :2. Dendrobatinw. — Arlioreal frogs of small size without 

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



Fig. 117. — Hylodes martinicensis. 

 1, an egg with embryo about seven 

 days old; 2, another, twelve days 

 old; S, the young frog just hatched; 

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

 Gadow, after Peters.) 



