A treatise on zoology . rd inneranterior process differentiated from the coracoid, ^vuown as themesocoracoid (precoracoid of Parker [317], Fig. 243), which maybe separately ossified. This mesocoracoid arch, although absent inrohjptems, is probably a primitive structure inherited from a common ancestor. A moredetailed study of the fossilgenera would throw light onthis question, which is of con-siderable importance in class-ification (Gegenbaur [153],Boulenger [42]). The essential features ofthe dermal pectoral girdlehave been described above(p. 214). It becomes muchmodified in the higher Actino
A treatise on zoology . rd inneranterior process differentiated from the coracoid, ^vuown as themesocoracoid (precoracoid of Parker [317], Fig. 243), which maybe separately ossified. This mesocoracoid arch, although absent inrohjptems, is probably a primitive structure inherited from a common ancestor. A moredetailed study of the fossilgenera would throw light onthis question, which is of con-siderable importance in class-ification (Gegenbaur [153],Boulenger [42]). The essential features ofthe dermal pectoral girdlehave been described above(p. 214). It becomes muchmodified in the higher Actino-pterygii. The two halves of theoriginally cartilaginous pelvicgirdle ossify, except in theChondrostei, in the form oftwo horizontal Ijones lyingin the abdominal wall, meet-ing ventrally in front, andbearing the fin-skeleton attheir hinder end (Figs. 244-248). The dorsal iliac processis scarcely if at all repre-sented. Small cartilages mayremain at the anterior endsof the bones, and rarely theto a small median cartilage. FlO. 245. Ventral view of the pelvic girdle and fins of Amiculm, Bou. The skeleton of the right tin is com-pletely exposed, dr, web of left tin with lepido-trichia; j), pelvic bone; , preaxial radial, orremains of axis. (Partly from Davidoff, from Micr. Sci.) two halves of the girdle may fuse to a{Gadus, Fig. 247). On very insufficient evidence it has been argued that theoccasional small anterior cartilages represent the true girdle, andthat the large pelvic bones are the modified basipterygia of the fins(Davidort[97-9], Gegenbaur [163], Wiedersheim [491-2]). WhileWiedersheim considered these cartilages to represent the first rudi-ments of a developing girdle, Gegenbaur, on the contrary, lookedupon them as its last vestiges. Since, however, the pelvic bonesare found normally developed in Teleostomes from the Devonianto the present epocli (Ensfheuoptcron, Fig. 244, Goodrich [173]), there CLASSIFICA TION 277 is no reason for rejecting the old \i
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