On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 339 
rounded, less than their own diameter apart (about four in two lines in the middle 
of the ray); they are a little wider at base than towards the apex, increasing in 
number downward by dichotomy ; the sides of each ridge are denticulated, with 
sharp recurved teeth extending half way across the intervening spaces, the denticle 
of one side connected with its fellow on the other by a slightly oblique fold across 
the ridge, each pair being separated from that above and below by about the 
thickness of the ridge; near the posterior margin on each side are four or five 
ridges much smaller than the rest, crossed by oblique blunt tubercles.” —M‘Coy. 
The ornamentation of the longitudinal ridges of this species bears a great 
resemblance to that of Ctenacanthus gradocostus, St. J. and W. (Geol. Survey of 
Illinois,” Vol. VL., p.425, pl. xv., figs. 2, 3); a reference to the enlarged drawing of the 
coste, loc, cit. pl. xv., fig. 3b, and comparison with Pl. XLIV., fig. 4a, representing the 
present species, will render this more clear than description. The ridges of the 
Quincy specimen are triangular in section, whilst those of C. denticulatus are 
rounded. The general form and character of the two species are similar as far as 
can be gathered from the imperfect specimens figured and described by Messrs. St. 
John and Worthen. 
Formation and locality : Dark shale above the Yellow Sandstone of Monaduff, Drumlist, N. Ireland, 
Ex coll. Woodwardian Museum, Cambridge. 
Ctenacanthus limaformis, Davis. 
(Pl. XLIV., fig. 5.) 
Spine, medium size, robust and strong, diameter large in proportion to its length. 
Specimen imperfect, a small part of the superior extremity is missing as well as a 
larger part of the base. The anterior margin of the spine is arched slightly, and 
along the whole of the exposed portion is a beard band of ganoine divided into 
small file-like segments, which appears to be the peculiar characteristic of this 
species. The length of the part preserved is 4°50 inches. 
Locality and formation : Mountain Limestone, Bristol. 
Ex coll. Earl of Enniskillen. 
Ctenacanthus salopiensis, Davis. 
(QEL ROI, kes ©) 
Fin spine, when perfect about ten inches in length, and at its broadest part 1°8 
inches in diameter. The base or part buried in the integument 1s large in propor- 
tion to the remainder, being nearly one-third the length of the spine. Its anterior 
margin curves rapidly towards the end and is 2°5 inches in length, the posterior is 
4°5 inches and considerably straighter. The line dividing the base from the upper 
portion of the spine is very oblique. The exposed part is slightly curved towards 
tke apex principally along its anterior margin. In transverse section the spine is 
triangularly elliptical, widest from back to front, much compressed at the sides ; 
the posterior diameter is greater than the anterior, the latter almost pointed. The 
