100 



Acthiopterijfjii — Cliondrostei. 



Wall-case, 

 No. 8, and 

 Table-cases, 

 Nos. 37 to 

 39. 



Order IT. — Actinopterygii. 



Suii-ORDER I. — Chondrostei. 



The earliest known ray-finned fishes are the Palfeoniscida^, 

 I'epresented in the Devonian by Cheirolepis. They exhibit a 

 very imperfectly ossified skeleton with heterocercal tail ; and 

 they must have Lad a persistent notochord. In their most 

 fundamental characters they agree Avith the modei-n sturgeons, 

 and are thus classed in the same sub-order (Chondrostei). 



Wall-case, 

 No. 8, and 

 Table-cases, 

 39, 40. 



l""iG. 141. — Ganoid sc:ilos of Eloit'ichlhyt utriatus, Ag. sp. ; Carboniferous. 



Nearly all of them, however, are covered with regular series 

 of scales, which are usually rhombic and nnited by a 

 peg-and-soeket articulation (Fig. 141). EloiiicJithys, Ehadi- 

 nichtJiys, and Gonatodus are the commonest Carboniferous 

 genera; I'alivnniscus (Fig. 142), Acrolepis, Amhlypterus, and 

 Pygopterus are Permian; (??/roZepzs is Triassic, and Atlierstcnila 

 is represented by a fine specimen from the Karoo Formation 

 (probably Triassic) of Cape Colony; Oxygnathus and Platy- 

 ftiagnm are Liassic ; and Cvccolepis ranges from the Lias to the 

 Purbeck Beds. 



The Platysomida? are deep-bodied fishes closely related to 

 the Pala^oniscidce, confined to the Carboniferous and Permian. 

 Uiiryjiotifs (Fig. 143) is Lower Carboniferous ; Cheirodns 



KiG. U'2.—ralaoniscn.f inacropoii its, Ag. (restoration by Dr. R. II. Traqiiair) ; 

 Kupferschiefer, Germany. 



and Mesolepis are best known in the Coal JNIeasures ; Vlatysomus 

 (Fig. 144) is both Carboniferous and Permian. 



