P0LYPTER1NI 



291 



osteology of the Polypterini ; Steindachner [4226], Budgett [67-8], 

 and Kerr [263] have contributed valuable knowledge of the larval 

 development of Polypterus. The two genera are essentially similar, 

 and since Polypterus is better known and appears to be less 

 specialised than Calamoichthys, it will here receive greater attention. 

 The body of Polypterus is fusiform ; that of Calamoichthys eel- 



Fig. 264. 



Polypterus bichir, Geoffr. A, two dorsal Unlets and neighbouring scales. B, much enlarged 

 view of a fragment of a scale with denticles. C, outer view of scale, enlarged, h.^'j anterior 

 articulating process ; a.s, surface covered by next scale ; b.s, basal scale of rinlet ; d, denticle ; 

 d.p, dorsal articulating process ; h.c, vascular canals ; I, lepidotrich ; p, lateral-line pore ; p.s, 

 exposed posterior surface bearing minute denticles ; r, endoskeletal radial ; sc, scale ; w, web 

 of fin ; ,i/.d, detached dentine cap of young denticle. 



like (Figs. 274, 275). In both the pectoral fin has a narrow base, 

 and a prominent lobe covered with scales on its outer side. The 

 lobe has a fringe of numerous lepidotrichia. It was to this superficial 

 structure that Huxley gave the name ' Crossopterygian ' ; but the 

 outward shape of the fin is of minor importance, and in its internal 

 skeleton it differs greatly from that of the acutely lobate fins of 

 Ceratodus, or even from the fin of Eusthenopteron (p. 282). The 

 pelvic fin has been lost in Calamoichthys. In Polypterus it is very 



