PISCES. 
81 
and even gigantic Coccosteus-Yike fishes from the Upper 
Devonian of North America. The head sometimes measures 
3 or 4 feet across, and one fragment of head-bone exhibited 
is nearly 4 inches in thickness. The teeth (Fig. 82) form 
powerful shears and pincers. The large collection of remains of 
Dinichthys, Gorgonichthys , Titanichthys , and allied genera in 
Wall-case 4 and Table-cases G to K was obtained by Dr. 
William Clark from the Cleveland Shale of Ohio. 
Homosteus (Hugh Miller’s “ Asterolepis of Stromness ”) 
is another Arthrodiran of moderate size with thin armour, 
from the Middle Old Eed Sandstone of Caithness, Orkney, and 
Russia, and is represented by plaster casts of fine specimens 
between Wall-cases 4, 5 (Fig. 83). Heterosteus is a gigantic 
allied fish, of which massive fragments from Eussia are 
shown in Wall-case 4. 
Phlyctcenaspis is the earliest and smallest Arthrodiran, 
from the Lower Devonian of England, Galicia, and Canada 
(Table-case G). 
Stjb-class IV.— Teleostomi. 
These are fishes with a bony armour or bony skeleton, or 
both; with a bony operculum covering the gill-cavity; and 
with the more or less hardened cartilages of the upper jaw 
not fused with the skull, but suspended from it behind. They 
are named Teleostomi (“ complete mouth ”) because external 
or membrane bones form a complete border to the jaws. 
They comprise the immense majority of known fishes. 
Order I.— CROSSOPTERYGII. 
Most of the early paddle-finned fishes already mentioned 
on p. 76 have their upper jaw suspended as just described, 
and may thus be regarded as the direct forerunners of the 
bony fishes proper. They are named Crossopterygii (“ fringe- 
finned ”) because their paddles are fringed with delicate fila¬ 
ments or fin-rays in the bordering skin. 
The fringe-finned ganoids are now almost extinct, being 
represented only in the fresh waters of Africa by Polypterus 
and Calamoichthys. In the Devonian and Carboniferous 
periods they existed in large numbers and great variety, and 
were distributed nearly all over the world. Holoptychius 
(Fig. 84) is a well-known Devonian genus represented in the 
G 
Wall-case 
4 . 
Wall-cases 
5 - 7 . 
Table-cases 
11 , 12 . 
