TAILLESS BATRACHIANS. 33 



are more developed than in others, and when many are placed close 

 together they form protuberant masses, sometimes on each side 

 of the neck (parotoids of Toads and Salamanders), sometimes on 

 the loin or on the hind legs, or on other parts of the body. There 

 is no doubt that in some species this secretion has more or less 

 poisonous properties ; that of the Common Toad is sufficiently dis- 

 agreeable to dogs, birds of prey, &c. to act as a protection to the 

 Batrachian ; but that of some South-American species (Bufo agua, 

 Dendrobates) is said to be a much more active poison, and to be 

 used by the Indians as one of the ingredients of their arrow- 

 poison. 



All the Batrachians which flourished in the older formations, 

 Carboniferous to Trias inclusively, belonged to the extinct order 

 Stegocephala or Lahyrinthodonta, and were succeeded in the Cre- 

 taceous by the Tailed, in the Tertiary by the Tailless Batrachians, 

 which order appears to have now attained its highest point of 

 development. No fossil Coecilian has as yet been found. 



Recent Batrachians are referable to three orders, viz. : — 



1. Ecaudata, Tailless Batrachians, such as Frogs and Toads; 



2. Caudata, Tailed Batrachians, such as Salamanders, Newts, 

 and Permanent Gill-breathers ; 



3. Apoda, Limbless Batrachians or Coecilians. 



Order I. ECAUDATA, or TAILLESS BATRACHIANS. 



This order, which comprises over 800 species, includes Batra- 

 chians destitute of a tail, with shortened body and four limbs, of 

 which the hinder pair is longest and adapted for leaping. 



Their skeleton shows many peculiarities. The following account 

 refers to the Frog : — The skull is large and flattened, with enormous 

 orbits ; the vertebral column shortened, with constantly eight prse- 

 sacral and one sacral vertebra, and a coccygeal style formed by the 

 ossification of the caudal notochord of the early stage of life. 

 The following is an enumeration of the principal bones of the 

 skull: — On the upper surface two large bones, the fronto-parietals 

 (fig. 23, fp), formed by the fusion of the frontals and parietals, 

 leaving uncovered anteriorly a portion of the ethmoid (e) ; a pair 

 of nasals {n) ; the prootic (po) on each side between the fronto- 



d2 



