ON SOME ARMOURED FISHES. 
23 
Fig. 2. A fragment of Pterospis t'ostratus showing well the 1 cancellated 
layer ’ ( b ) with its polygonal cavities, the letters correspond 
with those of Fig. 1. 
Fig. 3. Microscopic structure of shield of Pteraspis rostratus — a section 
cut parallel to the ridges. The vascular tufts and their connec- 
tion with the polygonal cavities ( b ) are well seen (Lankester). 
Fig. 4. Restoration of JEucephalaspis Lyelli (after Lankester). p = pec- 
toral; d = dorsal; c — caudal fins. 
Fig. 5. Restoration of Pterichthys Milleri, A g. Old Red Sandstone, 
Cromarty (after Pander) ; c, c, the pectoral fins. 
Fig. 6. Diagram figure of the Dermo-skeleton of the Sturgeon’s head 
(Acipenser sturio ), after Owen ; ch = the persistent notochord. 
EXPLANATION OF PLATE II. 
Fig. 1. Restoration of Coccosteus decipiens, Old Red Sandstone, Russia 
(after Pander) : ch the imdivided notochord ; n = neural spines ; 
h = haemal spines ; d = dorsal ; a = anal fin-rays ; c = the 
caudal fin. 
Fig. 2. Ceratodus Forsteri , *a living Dipnoid fish found in the rivers of 
Queensland, Australia (after Gunther). 
Fig. 3. Ostracion bicaudalis (the Trunk-fish), West Indies. Drawn from a 
specimen in the Zoological Gallery, British Museum. 
