J. W. DAVIS ON FISH-SPINES FROM THE LOWER COAL-MEASURES. 181 
13. Notes on Pruvropus Arrinis, sp. ined., Agassiz, and Du- 
SCRIPTION of THREE Sprnus of Cusrracronrs from the Lownr 
Coat-MuasurgEs. By J. W. Davis, Esq., F.G.8., F.S.A. (Read 
November 20, 1878.) 
[PuatTe X.] 
Two years ago I had the pleasure of reading a paper to this Society 
describing a thin stratum of shale known to extend over an area of 
several miles, immediately above the Better-bed coal in the neigh- 
bourhood of Clifton and Low Moor, south-east of Halifax. ‘The 
stratum averages from a quarter to three eighths of an inch in 
thickness, and is almost entirely composed of the fragmentary 
remains of fishes and Labyrinthodonts. Between thirty and forty 
species of fishes have been found, and are enumerated in the paper 
already referred to*. 
PLEURODUS AFFINIS, sp. ined., Ag. (PI. X. figs. 1-11.) 
Associated with these, several specimens of a peculiar Ichthyodo- 
rulite have been found during the last four or five years. Three 
of the specimens are well preserved, one of them nearly perfect 
and well separated from the matrix ; and there are also several 
others in a more or less broken condition. 
The length of the largest and most perfect example (fig. 10) is two 
inches and one tenth, and its greatest breadth, about the middle of the 
spine, is four tenths of an inch; from this point it tapers gradually 
in each direction to the basal and apical extremities. The anterior 
margin of the spine forms a gentle uniform curve from the base to 
the point ; on the posterior aspect the curvature is much more rapid 
from the point to the broadest part, thence it recontracts in an un- 
even line and ends in a somewhat rounded base about two tenths of 
an inch in diameter. The whole of the spine is much compressed 
laterally. The surface is marked by a series of fine longitudinal striae, 
fibrous in appearance, most distinctly marked on the basal end of the 
spine, and gradually disappearing towards the apex, which is quite 
smooth (fig. 11). Fully half the spine appears to have been buried 
in the integument or muscles of the fish. Along the back there is a 
cavity extending from the base one inch and three tenths, which 
probably enveloped and protected the dorsal fin. Higher, the cavity 
becomes enclosed and is ovate in form, remaining in a position 
much nearer the back than the front of the spine. 
Associated with these spines are numerous teeth, and there is 
eyery reason to believe that they have belonged to the same fishes. 
The teeth (figs. 1-8) are obliquely ovate in form, produced so as to 
form a coronal ridge along the longer axis ; the front part of the tooth 
is narrow, almost pointed, but becomes wider and more rounded back- 
wards. From the semi-pointed coronal ridge in the front part the 
* Quart, Journ, Geol, Soc. 1876, vol, xxxii, p, 532. 
Q.J.G.8. No. 138, g 
