SUB-CLASS V 



GAXOIDEI 



69 



Order 1. CROSSOPTBRYGII. Huxley. Fringe-finned Ganoids. 



Notochord persistent or vertebrae ossified. Tail diphy cereal or hetero-diphycercal. 



Infra clavicle present. Paired fins with a scab/ axis fringed on both titles by dermal 

 rays. BranchMegal apparatus between the rami of the mandible consisting of a 

 pair of large jugular plates, these in many Palaeozoic genera flanked by a series of 

 small lateral jugulars and an anterior median plate. Ganoid scales rhombic or 

 cycloidal, completely covering the trunk and. tail. 



Family 1. Holoptychiidae. Traquair. 



Body covered with imbricating, cycloidal ganoid scales. No ossified vertebrae. 



mmmim 



ffiW^i 



l|liiiiii^ :: ' 



Wmmmz 



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Fig. 124. 

 Holoptychius nobilissimus, Ag. Upper Old Red Sandstone ; Scotland (restoration after Huxley 



Pectoral fins acutely lobafe. Two dorsal fins and one anal fin, each borne by a single 

 i distally expanded support (axonost), followed by one or two rows 



of short basal pieces (baseosts), which support the very numerous, 



Fig. 125. 



Scale of Holoptychius 

 (Glyptolepis). Outer 

 (A), and inner (B) 

 aspect. Old Red Sand- 

 stout- : Wik, Russia 

 (after Pander). 



Fig. L26. 



Dendrodus biporcatus, Ag. Tooth in side view (A), and from below (B), nat. size, 

 and transverse section of the same (C), highly magnified (after Pander). 



fine, dermal fin rays. Lateral jugular plates, clavicle, and infraclavicle present. 



