SUB-CLASS V 



GANOIDEI 



69 



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



Nofochord persistent or vertebrae ossified. Tail dipliycercal or hetero-dipliy cereal. 

 Infraclavicle present. Paired fins with a scaly axis fringed on both sides by dermal 

 rays. Branchiostegal 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 

 cycloidcd, completely covering the trunk and tail. 



Family 1. Holoptychiidae. Traquair. 

 Body covered ivith imlricaUng, cycloidcd ganoid scales. No ossified vertebrae. 



Fig. 124. 

 Holoptychiiis nobUissinins, Ag. Upper Old Reil Sandstone ; Scotland (restoration after Hnxley 



Pectond fins acutely lobate. Two dorsal fins and one anal fin, each borne by a single 

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



of shi))t basal 2?ieces (baseosts), which support the very numefovs, 



Fig. 125. 



Scale of Iloloxitychius 

 (filyptolepis). Outer 

 (-4), and inner {B) 

 aspect. Old Red Sand- 

 stone ; Wik, Russia 

 (after Pander). 



Detulrodus liiporcatus, 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. 



