26 



FOSSIL FISHES. 



These are followed by the Rhizodontidce, represented by Tris- 

 tichopterus and QyroptycM'us (Fig. 38), from the Old Red Sand- 

 stone, and Rltizodus, from the Lower Carboniferous 

 of Scotland : to these succeed the Sanrodipteridce, 

 represented by Osteolepis (Fig. 39) and Diplopterus, 

 from the Old Red Sandstone; and Megalichthys, 

 from the Coal-measures. 



Strikingly remarkable in this case (Wall-case 6) 

 are the remains of Bhizodus Hibhei'ti, from Burdie 

 House, the huge teeth and detached bones of the 

 head of which led the earlier observers to refer it 

 to the Labyrinthodonts ; Bhizodus was probably the 

 largest of Palaeozoic fishes. 



Lastly, the Codacanilddce (Wall-case 7), remark- 

 able, as a family of fishes, for their long range in 

 geological time, Coelacanthus occurring in the Coal- 

 measures, the Permian and the Upper Oolite ; 

 Gi/rosleus in the Lias, TJndina in the Oolites (Fig. 41), and 

 Macropoma in the Chalk formation (Fig. 42). The walls of the 

 air-bladder appear to have been ossified in these fishes, as is well 

 seen in several specimens of the series of Macropoma. 



Fig. .",7.— Tooth 

 of Strepsodus. 



Fie. 41.— Undina Kohleri, Lias (restored outline after Huxley), a, Jugular plates ; ] 

 b, the ossified air-bladder ; c, the pelvic bones. 



2. The fossil representatives of the Acipenseroidei are as follows : 

 The Chondrosteidce, with a single genus, Chondrosteus, in the Lias 

 (Wall- case 7). 



Bony plates of Acipenser occur in the London Clay of Sheppey 

 (Wall-case 7) and in the Suffolk Crag. 



The Pala'oniscida (Wall-case 8, and Table-cases 37, 38, 39), in 

 which the body is covered with rhombic, ganoid, and often beauti- 

 fully sculptured scales, the caudal fin being completely heterocercal 

 and Sturgeon-like. 



