AMPHIBIA. 



287 



Opus includes the burrowing spade- 

 seen except at the breeding-season, 

 are Alytes and Bombifiator. The 

 Hylid^ have teeth, while the 

 tips of the toes are expanded into 

 sucking-disks. Our tree-toads be- 

 long to Hyla, Acris, and Choro- 

 philus ; Notodelphys and Nototrenta, 

 tropital America. The extinct 

 Pal^obatrachid^ (oligocene) 

 are noticeable for two sacral ver- 

 tebrae. 



ORDER III. FIRMISTERNIA. 



Tongue well developed ; epi- 

 coracoids firmly united in the 

 median line. The ENGYSTOMiDiE, 



foot toad which is rarely 

 Allied European genera 



Fig. 286. 

 ventral portion of 

 girdle of Rana, 

 heim, illustrating 



Sternum and 

 the shoulder 

 after Wieders- 

 t h e firmister- 



nous type of sternum, cl, clavicle ; co, cora- 

 coid ; ec, epicoracoid ; g, glenoid fossa ; os, 

 omosternum; s, ventral part of scapula; st, 

 sternum ; x, xiphisternum. 



Fig. 285. Shoulder girdle of 

 Bombinator igneus, showing the ar- 

 ciferous type, after Wiedersheim. 

 c, clavicle ; co, coracoid ; ec, epi- 

 coracoid ; g, glenoid fossa ; pc, pro- 

 coracoid ; s, scapula ; j-.r, supra- 

 scapula ; st, sternum. 



or toothless frogs, occur in 

 our southern states. Etigy- 

 stoma. The Ranid^, or 

 true frogs, have smooth 

 skin, and teeth in the up- 

 per jaw. Rana contains 

 our species including the 

 bullfrog (i?. catesbiana') 

 the largest known frog. 

 Rana first appears in the 

 miocene. Numerous other 

 families in the tropics, in- 

 cluding the Dendroba- 

 TiD^, which have toes like 

 the tree-toads, Hylidae. 



SUB-CLASS IV. GYMNOPHIONA (C^CILI.E). 



Limbless amphibia of worm-like shape ; tail lacking; vertebras 

 amphicoelous ; skull well ossified, with well-developed ethmoid ; 

 body externally ringed, and bearing semi-circular dermal scales. 

 Frequently a protrusible tentacle in a tentacular sheath between 



