100 



Act in opteryg ii hondros tei. 



Wall-case, 

 No. 8, and 

 Table-cases, 

 Nos. 37 to 

 39. 



Wall-case, 

 No. 8, and 

 Table-cases, 

 39, 40. 



ORDER II. Actinopterygii. 

 SUB-ORDER I. Chondrostei. 



The earliest known ray- finned fishes are the Paleeom'scidce, 

 represented in the Devonian by Clieirolepis . They exhibit a 

 very imperfectly ossified skeleton with heterocercal tail ; and 

 they must have bad a persistent notochord. In their most 

 fundamental characters they agree with the modern sturgeons, 

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



FIG. 141. Ganoid scales of ElonlcltUnjs xtriatus, Ag. sp. ; Carboniferous. 



series 



Nearly all of them, however, are covered with regular 

 of scales, which are usually rhombic and united by a 

 peg-and-socket articulation (Fig. 141). HJlonichthys, Ehadi- 

 nichthySj and Gonatodus are the commonest Carboniferous 

 genera; Palcconiscus (Fig. 142), Acrolepis, Amblypterus, and 

 Pygopterus are Permian ; Gyrolepis is Triassic, and Atlierstonia 

 is represented by a fine specimen from the Karoo Formation 

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

 siagnm are Liassic ; and Coccolepis ranges from the Lias to the 

 Purbeck Beds. 



The Platysomidse are deep-bodied fishes closely related to 

 the Palneoniscidaa, confined to the Carboniferous and Permian. 

 Eurynotus (Fig. 143) is Lower Carboniferous ; Cheirodus 



FIG. 142.Fahioniscus ina.cropon.us, Ag. (restoration by Dr. li. II. Traquair) ; 

 Kupferschiefer, Germany. 



and Mesolepis are best known in the Coal Measures ; Platysomus 

 (Fig. 144) is both Carboniferous and Permian. 



