. Zoology : for students and general readers . Zoology. AjYatomy of BATRACUIANS. 467 tinct Archegosaurtis had in its larval life branchial arches, and in fact so close are the affinities of some Amphibians to the Ganoids that it is probable that both types have had a com- mon origin ; while on the other hand the bones of certain extinct scaly Labyrinthodonts have been regarded by some authors as reptiles ; for example, the Carboniferous Miidodon- saurus was described as a reptile, but has been referred to the Amphibians by modern writers. The sternum or breast-bone (Fig. 429, s) first ajipears
. Zoology : for students and general readers . Zoology. AjYatomy of BATRACUIANS. 467 tinct Archegosaurtis had in its larval life branchial arches, and in fact so close are the affinities of some Amphibians to the Ganoids that it is probable that both types have had a com- mon origin ; while on the other hand the bones of certain extinct scaly Labyrinthodonts have been regarded by some authors as reptiles ; for example, the Carboniferous Miidodon- saurus was described as a reptile, but has been referred to the Amphibians by modern writers. The sternum or breast-bone (Fig. 429, s) first ajipears in the Batrachians. The shoulder-girdle is in great part carti- laginous. In the toads and frogs {Anura) the fore limbs, the radius, and ulna, and in the hind limbs the tibia and fibula, grow together ; there are four toes in the fore feet, and five toes in the hind feet. In the Siren the hind legs are fjj,. and Bhoulder-girdle wpiTifiTio- • in +lip pono-n-suakps °! ^™" ipr+wn nv tliTpp-fnprl side(s); d, clavicle ; e, episternum. Tlie eirner XWO or DUlCe loea. extreme shaded double portion below ;; The teeth of modern Ba- is "'e xipliisternum The cartilaginous parts are shaded.—After Gegenbaur. trachians are conical or lobate, and microscopically are simple, while those of the extinct forms are mostly complicated by the labyrinthine infolding of the walls, as seen in microscopic sections; the teetli of many Ganoids have a similar, though much simpler struc- ture. They are usually of the same size, and may be ar- ranged on projecting portions of different bones of the mouth, , the premaxillary, maxillary, mandibular, vomerine, pal- atine, and pterygoid bones, as in fishes. In tadpoles and in Sire7i the jaw-bones are encased in horny beaks like those of turtles and birds. In many Labyrinthodonts two tusks were developed on the palate. The nasal canal is much as in the Dipnoan fish, the internal opening being situated in the Perennibranchiates j
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
