196 VERTEBRATE ZOOLOGY 



ORDER III. ANURA (TAILLESS AMPHIBIA) 



The frogs and toads are the characteristic Amphibia of the present 

 age. They are represented by about 900 species and exhibit a very 

 pronounced adaptive radiation. They are the most highly specialized 

 of modern Amphibia and so much specialization exists within the 

 order that there is difficulty in listing characters that apply to all of 

 its members. Not only has there been adaptive radiation in the order, 

 but all of the large families exhibit a radiation into terrestrial, arboreal, 

 aquatic, and burrowing types. Since the frog is a favorite type ver- 

 tebrate and is used in nearly all elementary courses in zoology, it will 

 save time and space to omit any detailed anatomical description of a 

 type form. We shall therefore proceed to give an abbreviated sys- 

 tematic survey of the various groups of Anura. Two suborders are 

 distinguished: the Aglossa, which are without a tongue and have 

 eustachian tubes united in one pharyngeal opening; and the Phaner- 

 oglossa, in which a tongue is present. The first is a coherent natural 

 group, but the second may be an artificial assemblage. 



SUB-ORDER I. AGLOSSA 



This is a small group of frogs not well known to the layman. Three 

 genera, Pipa, Xenopus, and Hymenochirus occur. Of these Pipa is a 

 South American tropical form and the other two belong to Africa. 



Pipa americana (the Surinam toad) is a classic object to the zoolo- 

 gist on account of its unique breeding habits (Fig. 114, A). The crea- 

 ture is an odd, ugly aquatic toad, with exceedingly large hind feet and 

 a very short, broad head. The following description of its spawning 

 is described by Bartlett: "About the 28th of April the males became 

 very active and were constantly heard uttering their most remarkable 

 metallic call-notes. On examination we then observed two of the 

 males clasping tightly around the lower part of the bodies of the 

 females, the hind parts of the males extending beyond those of the 

 females. On the following morning the keeper arrived in time to 

 witness the mode in which the eggs were deposited. The oviduct of 

 the female protruded from the body more than an inch in length, and 

 the bladder-like protrusion being retroverted, passed under the belly 

 of the male on to her own back. The male appeared to press tightly 

 upon the protruded bag and to squeeze it from side to side, apparently 

 pressing the eggs forward one by one on to the back of the female. By 



