80 GUIDE TO THE FOSSIL REPTILES, AMPHIBIANS, FISHES. 
Wall-ease 
4. 
Table-eases 
G-K. 
Their remains occupy Wall-case 4, and the characteristically 
jointed neck is especially well seen in two mounted skulls 
of Dinichthys. 
Coccosteus (Fig. 81), which attains a maximum length of 
about two feet, is the best known Arthrodiran, and is repre¬ 
sented by a fine series of specimens from the Middle Old 
Eed Sandstone of Scotland. All the armour-plates are 
Fig. 83.—Upper view of armour of Homosteus milleri, from the Middle Old 
Red Sandstone of Caithness ; one-sixth nat. size. A. B. C. undeter¬ 
mined bones; a.d.l. anterior dorso-lateral; a.e. ethmoid; c. central; 
e.o. external occipital ; ra. marginal; m.d. median dorsal; m.o. 
median occipital; o. orbit; p.d.l. posterior dorso-lateral; p.o. pre¬ 
orbital ; jpt.e. pineal; pt.o. post-orbital. The double lines indicate 
the course of the slime-canals. (After R. H. Traquair. Wall between 
Wall-cases 4, 5.) 
deeply overlapping, but those of the trunk are ^confined to 
its front part just behind the head. The slightly hardened 
spines above and below the space which would originally 
be occupied by the notochord, as also the supports of the 
membranous dorsal fin, are seen in the naked trunk. There 
are plates which might have supported pectoral fins if suoli 
were present; and there are distinct remnants of a pair of 
posterior or pelvic fins. Dinichthys and its allies are large 
