6 



When limbs are present they have the same skeletal elements as the 

 limbs of reptiles and mammals. Some batrachians are devoid of limbs. 

 All of our species have the anterior limbs present ; most of them have 

 also the posterior pair. The anterior limbs never have more than four 

 fingers ; the posterior may have five toes. 



Not much can be said here regarding the skeleton. The vertebrae are 

 usually either amphicoelous or opisthocoelous. Ribs are often absent; 

 when present they do not connect with a sternum below. In the lower 

 forms as many as four branchial arches may be present ; in the higher 

 species the number is reduced. There may be teeth on the maxillaries, 

 premaxillaries, vomers, and dentaries ; more rarely on the palatines, 

 the pterygoids and the splenials. A baud of teeth may be found in 

 some cases supported by the parasphenoid. The teeth are almost al- 

 w^ays very simple in structure, pointed, and grown fast to the support- 

 ing bones. 



Bi*eathing is effected in the adult by drawing the air inlo the mouth 

 through the nostrils, then closing these, contracting the cavity of the 

 mouth, and thus forcing the air into the lungs. Hence, a frog may be 

 suff^ocated by holding its mouth open. 



For additional information on the anatomy of the Batrachia the 

 student should consult Prof. Huxley's article, "Amphibia," in the En- 

 cyclopedia Britanica ; also for the Urodela, Dr. R. Wiedersheim's work, 

 ^'Kopfskelet der Urodelen." 



The living species of Batrachia have been divided by Prof. E. D. Cope 

 (51, 13) into four orders, viz: Proteida (Nedurus), Urodela, Trachy- 

 stomaia (Siren), and Salientia. I prefer here to retain the genera Nee- 

 turns, t^roteus and Siren under the Urodela. 



Key to the Orders of Batrachia 



A. Liml)s present or absent; when present, the hinder pair not much 

 more strongly developed than the anterior. Tail developed or 

 not ; present iu all our species. Animals fitted for creeping on 

 or burrowing in the earth or for swimming in the water. 



Urodela,-]^. 6. 



AA All four limbs present and the hinder pair greatly developed. 

 Tail wholly absent in the adult Animal, when on land, usu- 

 ally progressing by leaping. Salientia, p. 48. 



Order URODELA. 



« 



Batrachia having a lizard-like, eel-like, or serpent-like form. All limbs, 

 as well as the supporting girdles, absent in the extralimital Cfecilidce. At 

 least the fore limbs and the shoulder girdle present iu all our forms; and 

 usually also the hinder limbs. Posterior limbs never conspicuously 



