DAVIS : DISTRIBUTION OF FOSSIL FISHES. 
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ganoine, with powerful jaws armed with large pointed teeth, 
evidently a piedaceous fish, feeding probably on its smaller asso- 
ciates. Along with the Megalichthys there is frequently found a 
still larger ganoid, Rhizodus, which is known to be sixteen or 
eighteen feet in length, though the Yorkshire specimens are much 
smaller. In these coal measures it has only been found in one 
locality, above the Black-bed coal near Bradford ; but in Scotland, 
at Gilmerton, it is of frequent occurrence, and teeth are in my 
collection which measure quite four inches in length, and scales of 
nearly the same diameter. The teeth and scales of Strepsodus 
(or Holoptychius) are generally found along with other fish 
remains in Yorkshire. The teeth of this fish have a peculiar twist 
towards the point which readily distinguishes them from any other 
species ; they frequently occur nearly or quite two inches in length. 
The scales appear to have been softer and more loosely attached 
to each other than is usually the case with ganoids, resulting in 
their separation before becoming fossilized ; consequently, speci- 
mens are rarely found of more than single scales, though one slab of 
shale about sixteen inches by ten, covered with scales and a large 
operculum, seemingly in proper position, indicates that the fish 
must have been several feet in length. The remains of Coelacanthus 
are very abundant in the Yorkshire measures, decidedly the 
most frequent and characteristic fish of the period. In the lower 
coal measures it is not so well preserved or so common as in those 
higher up the series. In the shale above the Better-bed coal it is 
never found entire, but the bones of the head indicate a fish of 
about two feet in length. It is present in great abundance in the 
Cannel coal between Wakefield and Bradford, and is well and 
beautifully preserved. The specimens are of varied size, ranging 
from two and three inches to between eighteen and twenty-four 
inches. Associated with these ganoids were those of the genera 
Acrolepis, Platysomus, Rhizodopsis, and others which are occasion- 
ally found in exquisite preservation, but more frequently in 
fragments. One other ganoid should be noticed, though of com- 
paratively rare occurrence in this coal-field it is more frequently 
