SUB-CLASS V 



GAXOIDEI 



81 



145). Trunk much laterally compressed, deeply fusiform or cycloidal. Ex- 

 ternal bones ornamented with tubercles and ridges of ganoine. Eye surrounded 

 by a complete ring of small quadrangular plates (co), behind which are from 

 five to eight postorbitals (so, cheek- 

 plates). The supra-temporal plates (st) 

 also numerous. Operculum, suboper- 

 culum, and interoperculum large, 

 arranged in an arch. Preoperculum 

 narrow, almost or completely covered 

 by the postorbitals. A median gular 

 plate between the laminar branchiostegal 

 rays. Fin-fulcra A-shaped, the two 

 halves being fused at the apex. Pectoral 

 and pelvic fins small ; dorsal and anal 

 fins much extended and opposed ; caudal 

 fin slightly forked. Scales on the middle 

 of the flank deeper than broad ; no 

 prominent ridge scales ; all the scales 

 thick and enamelled, sometimes tuber- 

 culated. The earliest species in the 

 Alpine Trias (Seefeld, St. Cassian). 

 Common in the Lower Lias of England 

 and the Upper Lias of Wiirtemberg 

 (Boll, Holzmaden), Bavaria (Banz), 



Fig. 145. 



Head of Dapedius, ag, Angular; br, ijalai plate; 



bf, Branchiostegal rays ; d, Clavicle ; co, Circuin- 



orbitals ; d, Dentary ; /, Frontal ; iop, Interoper- 



Xorthem France (Calvados), (D. pholi- culum; mx, Maxilla; na, Nasal; op, Operculum; 



7 , A ,-. , , /-\ , \ a i or > Orbit; p, Parietal; pmx, Premaxilla ; vt, Post- 



dOtllS, Ag. j V. CaelatllS, Querist.). AlSO temporal; scl, Supraclavicle ; so, Suborbitals; sop, 



Suboperculum ; sg, Squamosal ; st, Supratemporal 



found 

 India. 



in the Gondwana Beds of 



(after Traquair). 



Heterostrophus, Wagner. Lithographic Stone (Upper Jurassic) ; Bavaria. 



Cleithrolepis, Egerton. Hawkesbury Formation ; New South Wales. 

 Karoo Formation ; Orange River Colony. 



Tetragonolepis, Bronn (Pleurolepis, Quenst.). Small oval or almost cycloidal 

 fishes, laterally compressed, with small pectoral and pelvic fins. Dorsal and 

 anal fins much extended. Scales deepened on the flank, their front border 

 thickened and forming a vertical ridge. T. semicindus, Bronn, from L^pper 

 Lias, Wiirtemberg and Bavaria. Other species in the Upper Lias of England, 

 and the Kota Formation of the Deccan, India. 



Family 2. Semionotidae. Woodward. 1 



Premaxilla, maxilla, and dentary with obtusely conical or chisel-shaped teeth; 

 vomer, pterygopalatine arch, and splenial with several rows of stouter hemispherical 

 teeth. All fins fringed with fulcra. Caudal fin hemi-heterocercal. Scales thick and 

 rhombic. Trias to Cretaceous. 



Colobodus, Ag. (Asterodon, Miinst. ; Tholodus, Meyer ; Dactylolepis, Kunisch). 

 Teeth hemispherical and irregularly crowded, usually with a mammiform eleva- 



1 Quenstedt, F. A., Ueber Lepidotus in Lias e. Tubingen, 1847. — Sauvage, II. E., Memoire stir 

 les Lepidotus maximus et palliatus (Mem. Soc. geol. France, ser. 3, vol. I.), 1877. — Meyer, H. von. 

 Fossile Fische aus clem Muschelkalk (Palaeontogr. vol. I.), 1850. — Dames, W., Die Ganoiden des 

 deutschen Muschelkalks (Palaeont. Abhandl. vol. IV.), 1888. — Branco, W., Ueber eine neue 



Lepidotus- Art aus dem Wealden (Jalirb. 

 VOL. II 



preuss. geol. Lahidesanst.), 1885. 



G 



