238 
DAVIS : DISTRIBUTION OF FOSSIL FISHES. 
great number of genera and species as, well as individuals, of fossil 
spines. The genera Gyracanthus and Ctenacanthus are common 
to all the localities, occuring in greater or less abundance, but the 
genera Lepracanthus, many of the species of Pleuracnthus, the 
genera Phricacanthus, Hoplonchus, and Compsacanthus have 
hitherto been peculiar to the Yorkshire coal-field. The great 
abundance of Coelaeanthus may be also considered a peculiarity of 
this district, for, though the fish is found in Staffordshire and else- 
where, it is comparatively rare. 
The Staffordshire district has been particularly rich in species 
of small ganoids. Palceoniscus (Elonichthys), which occurs in 
Yorkshire very sparingly, if at all, is extremely abundant and well 
preserved. The genera Platysomus, Cycloptychius, Acanthodes, 
and Amphicentrum are all well represented, as well as several 
others. 
The Newcastle district is remarkable for the number and pre- 
servation of several species of Ctenoclus, whilst Paloeoniscus is 
rare, and the spines so common in Yorkshire are very rare, A larger 
proportion of Labyrithodonts are found intermingled with fish 
remains in this coal-field than in any other. Whilst on the other 
side the Tweed the principal feature of the fish-fauna rests in the 
presence of immense ganoids of the genus Khizodus ; these fishes, 
armour plated and possessing strong jaws armed with immense 
teeth measuring three or four inches in length, must have been 
most formidable adversaries to all other existing species. In no 
other district is the Khizodus developed to so large a size as in the 
South Scotch coal-field. Thus we find that, whilst certain of the 
fishes are common to all the districts, like Megalicthys, Gryracan- 
thus, and Ctenacanthus, there are others vvhich were altogether 
localized, or which thrived much better in some localities than 
others. It will be an interesting work, when sufficient material 
shall have been accumulated from all these districts, to consider on 
waat special features these diversities of fauna depend, and to en- 
deavour to elucidate by these means the physical history of the 
carboniferous period. 
