SUB-CLASS V 



(iAXOIDEI 



85 



Fig. 151. 



I'holidopleurus typus, Bronn. Keuper ; Raibl, Carinthia. 

 2/3 nat. size (after Kner). 



series short and very deep on the flank, those on the back and ventral 

 region longer than deep. Dorsal and anal fins delicate, elongated, and low, 

 directly opposed on the hinder part of the caudal region. Caudal fin ex- 

 ternally homocercal, slightly forked. Trias ; Raibl, Carinthia. 



Pleuropholis, Egerton. Upper Jurassic (English Purbeck Beds, and French 

 and Bavarian Lithographic 

 Stone). P. egertoni, Wagn. 



Pholidophorus, Ag. (Figs. 

 152, 153). Body shaped like 

 a carp. Scales thin, deeper 

 than long on the flank, en- 

 amelled, smooth or finely 

 striated and serrated. Small 

 dorsal fin opposed to the pelvic 

 pair. Caudal fin externally homocercal, deeply forked ; • a large, unpaired 



dorsal scale often at its base. Com- 

 mon in the Alpine Trias of Raibl 

 (P. bronni, Kner) and Seefeld ; in 

 the Lias of Lyme Regis (P. bechei, 



Ag., P. lim- 

 batus, Ag.), 

 Whitby, Cal- 

 vados, Wur- 

 temberg, and 

 Bavaria (P. 

 germ aniens, 

 Querist.) ; in 

 the Lithogra- 

 phic Stone of 

 Bavaria and 

 France ; in 

 the Purbeck 

 Beds of England and Lower Jura of the Black Hills, South Dakota. 



Isopholis, Zittel. As Pholidophorus, but scales of equal size and rhombic. 

 Pectoral and anal fins large. Lithographic Stone of Bavaria and France. 



ii«. 



PJiolidophorus striolaris, Ag. Head, nat. size. Upper 

 Jurassic (Lithographic Stone) ; Eichstadt. cl, Clavicle ; 

 jr., Frontal ; iop, Interoperculum ; mil, Mandible ; mx, 

 Maxilla ; na, Nasal ; op, Operculum ; pa, Parietal ; pmx, 

 Preniaxilla ; pop, Preoperculum ; psp/i/Parasphenoid ; pt, 

 Post-temporal ; sd, Supraclavicle ; so, Suborbitals ; sop, 

 Suboperculum. 



Fig. 153. 



Pholidophorus ptisillus, Ag. 

 Rhaetic ; Seefeld, Tyrol. 

 Nat. size. 



Faniilv 6. Pycnodontidae. 



Agassiz. 



Trunk laterally compressed, very deep, oval. Notochord persistent. Bibs, vertebral 

 arches, and spines well ossified. Opercular apparatus incomplete, mill one or two 

 h'anchiostegal rays. Premaxilla with two to four prehensile front teeth; maxilla 

 thin, deepened behind, toothless ; palatine and vomerine bones fused together, •usually 

 with five longitudinal series of round or oval grinding teeth ; splenial of mandible 

 large, with coronoid p>rocess, and three, four, five, or more rows of grinding teeth ; 

 dentary small and terminal, fitting in a groove of the splenial, "ml bearing two to four 

 prehensile front teeth. Branchial arches with very numerous, closely arranged, bony 

 filaments. Clavicle broadly ovate at the lower end. Fin fulcra absent. Pelvic fins 

 small. Dorsal and anal fins much extended. Scales deeper than long, with a 

 thickened, ridge-like anterior margin. Lower Lias to Upper Eocene. 



Gyrodus, Ag. (Figs. 154-157). Trunk completely covered w T ith scales. 



