On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 337 
lateral tubercles ; in certain irregular spots these lateral tubercles increase in size 
and strength, and distinctly cross the ridges by becomiug connected across them ; 
in several of the ridges, particularly towards the base, the transverse tuberculation 
and notching becomes so distinct, that the ridge is separated into a row of 
triangular tubercles about half a line long. 
“The extreme irregularity of the ridges of this species, no two of them being 
quite alike, and several of them totally changing their aspect after short distances, 
easily distinguish this species from its congeners. The finely striated base is of 
rather small size, and rapidly tapering, the line of separation between it and the 
ridged exterior being very oblique.” 
The specimens which served Prof. M‘Coy as types for this species, appear from the 
figures which he has given to have consisted of a few detached fragments of the 
spines. Since that description was written, many specimens have been obtained from 
the limestone at Armagh, and I am enabled to give drawings of perfect specimens, 
by the kindness of Lord Enniskillen. The specimen (PI. XLIV, fig. 1) is five 
inches in length, its greatest breadth being ‘8 of an inch, from which point it tapers 
in either direction, gradually, towards the superior extremity, ending in an acute 
point, and more rapidly towards the base, which is obtusely rounded. The exposed 
portion of the surface, extends three inches from the point along the anterior 
margin and is divided from the base by an oblique line, extending to the posterior 
margin, which it reaches at a distance of 2:2 inchesfrom the apex. The base is smooth, 
or finely striated and occupies an area almost equal to that of the exposed part. 
Along the posterior margin, on each side, there is a row of obtusely rounded denticles. 
A peculiarity not observed by M‘Coy in the arrangement of the longitudinal 
ridges is, that they extend parallel with the pcsterior margin, which is almost 
straight, whilst those nearer the front of the spine run out along the anterior margin. 
Formation and locality : Mountain Limestone, Armagh. 
Ez coll. Kar] of Enniskillen. 
Ctenacanthus brevis, Agass. 
(Pl. XLIIL, fig. 3.) 
Ichthyodorulithes brevis, Buckl. and De la Béche (MS.) 
Ctenacanthus brevis—L. Agassiz, 1837. ‘‘Rech. Poiss. Foss.,” Vol. IIL., p. 11, pl. in, fig. 2. 
” 9 C. G. Giebel, 1848. “Fauna der Vorwelt,” Vol. I1., p. 309. 
” »  H.G. Bronn, 1848. ‘“ Nomencl. Paleont.,” p. 355, 
” ” » 1849. “ Enumerator Paleont.,” p. 649. 
” 3 F. J. Pictet, 1854. “Traité de Paléont.,” Vol. II., p. 299. 
” » J. Morris, 1854, “Catal. Brit. Foss.,” p. 323. 
53 5 Morris and Roberts, 1862. “Quart. Jour. Geol. Soc.,” Vol. XVIII. p. 100. 
op % Youngand Armstrong, | 871. “Trans. Geol.Soc., Glasgow,” Vol. III, Supt.p. 70, 
= Armstrong, Youn ” 
z and Robertson’ ¢ 1876. “Catal. West. Seot. Foss.,” p. 61. 
” re) J. J. Bigsby, 1878. “Thesaurus Devon.-Carb.,” p. 351. 
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