406 



ZOOLOGY. 



Labyrinthodonts such as Rliiacliitomus, the vertebrae are- 

 ossified, but the centra consist of three pieces. In Cricotus- 

 there are two kinds of bodies, centra and intercentra. The 

 ribs arc rudimentary, except in the blind-worms (Ccecilia). 

 The skull is usually broad and flattened ; it differs from 

 that of fishes in having no bones representing the operculum, 

 suboperculum, interoperculum, or branehiostegal bones ; but 

 a membrane bone probably homologous with the preopercu- 

 lum is said to exist. The maxillary are usually and the pre- 

 maxillary bones always present, usually armed with teeth ; no 

 Batrachian possesses a complete basioccipital, supraocci- 



pital, basisphenoid, ali- 

 sphenoid, or presphe- 

 noid cartilage bone; 

 while "the frog's skull 

 is characterized by the 

 development of a very- 

 singular cartilage bone, 

 called by Cuvier the ' os- 

 en ceinture,' or gi; die- 

 bone." (Huxley.) 



The embryonic carti- 

 lage persists in the low- 

 er jaw in adult Batra- 

 chians as in fishes, and 

 Fig 428.-skeieton of a Frog, a, skull ; f>, bony parts are developed 



verlelirse ; c, sacrum, and e, its continuation > ' _ 1 



(nrostyle);/, suprascapula; )7, hiunerns; A, fore- m connection With it 

 arm bones ; i, wrist bone* (carpala and meta- . 



carpals) : </, ilium; >, thi<:h U'emur) ; ?(, \eg which CSSeiltially CO1T6- 

 bonc (ulna) : o, elongated first pair of ankle- , , ,, , 



bcnu-s itarsals) ; ;;, 5, foot bones or phalanges. SpOllCl to tllOSC OI nshes. 



After Owi n. //-^ i \ 



(Gegenbaur. ) 



The suspensoriuni is immovably joined to the skull, and 

 with it is connected the hyoidean arch. The branchial 

 arches in the tailed forms persist in varying numbers, i. e., 

 from two to four, but are dropped in the toads and frogs. The 

 skulls of certain Labyrinthodonts are roofed -in by broad, 

 flat bones, so that they bear a strong resemblance to certain 

 Ganoids represented by the garpike, while Gegenbaur states 

 that there are many bony parts in the skull of the Batra- 

 chians which resemble those in the Dipnoan fishes. The ex- 



