Looe: ! J. W. DAVIS ON FISH-SPINES FROM 
sides are spread out from the base to about the same width as the 
hinder portion of the tooth. These lateral wing-like processes are 
cut or notched transversely to the axis of the tooth. The notches 
vary in number from four to cight. There is also considerable 
variation in the form of the teeth themselves ; some are narrower, 
others broader, in proportion to their length. An average tooth is 
from six to eight tenths of an inch in length, the breadth equalling 
half the length. The majority are covered with a greyish-white 
enamel and are ornamented with inosculating delicate transverse 
ridges which occasionally assume a reticulated character, especially 
near the edge of the lateral process. In a large proportion a finely 
pitted or punctured surface takes the place of the ridges; and more 
rarely the two are combined and give a most exquisite texture to the 
enamel. The anterior central part of the coronal ridge is frequently 
worn down to a flat surface in the larger and apparently older teeth ; 
and in the teeth exhibiting this character a much greater degree of 
curvature may be noticed ; the tooth, the base of which is, as a rule, 
rather flat, assumes quite a crescent shape, as in Pl. X. figs. 6-8. 
By the kindness of Mr. J. Ward, of Loughton, I have been able to 
compare my specimens with two or three from the Staffordshire coal- 
field. One of these is in connexion with a few fragments of teeth, 
which are probably those of Helodus simplew, Ag. ; and if this be the 
case, there is certainly a great resemblance between the two sets of 
spines. The teeth of Helodus, however, are almost unknown in the 
Bone-bed, whilst nearly two hundred teeth of Pleurodus are in my 
possession, which have been found in immediate juxtaposition with 
the spines. That the latter are the spines of Plewrodus receives some 
support from the fact that Messrs. Hancock and Atthey found in the 
Coal-measures at Newsham a small spine connected by shagreen with 
the teeth of Pleurodus Kankinii. The specimen is described in 
Nat. Hist. Trans. of Northumberland and Durham, vol. iv. part 1. 
page 408. From the illustration which accompanys the description 
of the fish-remains, the spine appears to be imperfect, and has lost 
the basal part ; in other respects it bears a very exact resemblance to 
the exposed part of the spines from Clifton. 
Itis described as being five eighths of an inch in length and situated 
at the anterior extremity of the dorsal fin. The fish is represented 
as being a little more than three inches from the head to the tail, and 
nearly two inches in depth a little behind the head. The position 
of the head is indicated by the presence of teeth, which are in a 
disturbed condition and probably about ten or twelve in number. 
No bones are distinguishable, the skeleton having been entirely 
cartilaginous. The whole of the specimen is covered with shagreen, 
the tube rcles being very minute and much scattered. The teeth 
are two tenths of an bal long, “ boss-like in form, somewhat elongated, 
and ridged or carinated along the longer axis; the sides are con- 
siderably expanded in the centre, the expansions dying out towards 
the end of the tooth.” A specimen, twice the size of this, is men- 
tioned as having been found at Kenton, which, it is suggested, may 
belong to another species. 
