ORDER GANOIDEI. 977 



cranial bones are covered with ganoine, and mostly sculptured ; the 

 mouth is large ; the first branchiostegal rays form jugular plates ; 

 there is a row of median V-shaped scales on the superior surface of 

 the extremity of the body ; and the teeth are small, conical, or cylin- 



Fig. 914. — Left lateral view of the skull of Palaoniscus macro pomus', from the Permian, p, 

 Parietal \ f, Frontal; sq, Squamosal; s.t, Supratemporal ; fi.t, Posttemporal ; e, Ethmoid; a.f, 

 Prefrontal ; pmx, Premaxilla ; mx, Maxilla ; co, sa, so, Suborbitals ; d, Dentary ; op, Oper- 

 cular ; p.op, Preopercular ; iop, Subopercular ; br, Branchiostegals ; cl, Clavicular; scl, Supra- 

 clavicular ; pel, Postclavicular ; id, Infraclavicular ; or, Orbit. (After Traquair.) 



drical, and rarely plicate at the base. The chief characters of the 

 bones of the skull and of the secondary pectoral girdle are shown in 

 fig. 914, in which it will be seen that the preopercular covers a por- 

 tion of the face above the large and broad maxilla. Dr Traquair 

 observes that if a Palaeoniscid were stripped of its scales and fur- 

 nished with a long snout, it would be so like Poly don that there 

 would be no doubt as to their near relationship ; and he further 

 remarks that the one row of V-shaped scales found on the dorsal 

 side of the extremity of the body in Polyodon is identical with the 

 row of scales occupying the same position in Palczoniscus. This 

 leads to the conclusion that the existing Sturgeons are the survivors 

 of a series of Ganoids, now totally lost, which formerly gave off the 

 Palceoniscidoz and Platysomidce. as specialised branches. 



This family embraces such a large number of genera, that space 

 permits of but little more than their bare enumeration. In the 

 Devonian Chirolefiis, found both in Europe and Canada, the body 

 is slender, and the fins are large, with the rays very finely divided ; 

 while Rhabdolepis (fig. 915) of the Rothliegendes (Lower Permian), 

 while having fins of somewhat similar structure, is distinguished by 

 the deeper and more spindle-shaped body. Cosmoptyckws, of the 

 Scotch Carboniferous, is allied to Rhabdolepis, but has the anal fin 

 with a longer base. In the type genus Palczoniscus (figs. 914, 916) 

 the body is much elongated, and the fins are very small and widely 

 separated. It occurs in the Kupfer-Schiefer and Magnesian Lime- 



