466 



ZOOLOGY. 



Labyrinthodonts such as Rhiacliitomus, the vertebra are 

 ossified, but the centra consist of three pieces. In Cn'cofus 

 there ai-e two kinds of bodies, centra and intercenfra. The 

 ribs are rudimentary, except in the blind-worms {Cwcilia). 

 The skull is usually broad and flattened ; it diifere fi-om 

 that of fishes in having no bones representing the operculum, 

 suboperculum, interoperculum, or branchiostegal bones : but 

 a membrane bone probably homologous with the preopercu- 

 Inm is said to exist. Tlie maxillary are usually and tlie pre- 

 ma.\illary bones always jnesunt, usually armed with teeth ; no 

 Batrachian possesses a complete basioccipital, supraocei- 



pital, basisphenoid, ali- 

 sphenoid, or presphe- 

 noid cartilage bone; 

 while '-the frog's skull 

 is characterized by the 

 dcTelopment of a verv 

 singular cartilage bone, 

 called by Cuvier the " ('■*- 

 en ceintiire,' or gii die- 

 bone."' (Huxley.) 



The embryonic carti- 

 lage persists in the low- 

 er jaw in adult Batra- 

 chians as in fishes, and 



Fie. 4K.— Skeleton of a Prog, a, skoll ; 6, T,Onv Darts nvp rlpTplrmMl 

 vertebra; c sacnini, and e, its continuation . "j pat 1= aie ue^eiopeu 

 (nrostyie): /', i'uprascapilla : ^, humerus; A, fore- ]ji Connection "with ifc 

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

 carpals) ; d, ilium ; ni, thisrh ifemnr) ; n, leg which CSSeiltiallv COrrC- 

 bone (nlua) : o, elongated first pair of ankle- , '- /? i 

 bones (tarsals) ; p^g^ foot bones or phalanges, spond tO tllOSe of fisheS. 

 —After Uwi a, " r-i , \ 



(uegenbaur.) 

 The suspensorium is immovably joined to the skull, and 

 with it is connected the hyoidean arch. The branchial 

 arches in the tailed forms persist in var^incr numbei-s, (. e., 

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

 skulls of certain I.abyriuthodouts are roofed in by broad, 

 flat bones, so tbat 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 Bati-a- 

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



