PISCES. 
85 
degenerate sturgeons (Fig. 94). Such fishes are appropri¬ 
ately named Chondrostei (“ gristle-boned ”). 
The earliest Chondrosteans are the Palaeoniscidae, which Wall-case 
are rapacious fishes with complete jaws, well-formed external T abl ®' cases 
head-bones, and usually a regular covering of enamelled 13 - 15 . 
rhombic scales, united by peg-and-socket joints (Fig. 89). 
Cheirolepis is their oldest known 
representative, from the Middle 
Old Eed Sandstone of Scotland 
and the Upper Devonian of 
Canada (Wall-case 8), but they 
are specially characteristic of Car¬ 
boniferous and Permian forma¬ 
tions. Palceoniscus itself (Fig. 
90) is Upper Permian (Table-case 
14). Elonichthys , Bhadinichthys, 
and Gonatodus are the common¬ 
est Carboniferous genera; Acro- 
lepis, Amblypterus, and Pygopterus 
occur with Palceoniscus in the 
Permian; Gyrolepis is Triassic, and Atherstonia is abundant 
in the Karoo Formation of South Africa (Table-case 15) ; 
Oxygnathus and Platysiagum are Liassic (Wall-case 8); and 
Coccolepis ranges from the Lias to the Purbeck Beds (Table- 
case 15). 
The Platysomidae are deep-bodied fishes with stumpy 
Fig. 89. —Ganoid scales of Elon¬ 
ichthys striatus, outer view (a) 
and inner face (b), from the 
Lower Carboniferous of Scot¬ 
land ; nat. size. The inner 
face shows the peg-and-socket 
articulation. 
Fig. 90.— Restoration of Palceoniscus macropomus, from the Upper Permian 
of Germany; nearly one-half nat. size. (After R. H. Traquair. Table- 
case 14.) 
teeth, closely related to the Palseoniscidse, but confined to Wall-case 
Carboniferous and Permian rocks. Eurynotus (Fig. 91) is Tabl ®; cases 
Lower Carboniferous, while Platysomus (Fig. 92) is both 15,10. 
Carboniferous and Permian. 
The Catopteridae are small Triassic Chondrosteans in which 
