On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 335 
p. 68, pl. vii., fig. 1), both on account of their size, their general form and the 
character of their external decoration. The description of the spines given by Dr. de 
Koninck is almost identical with that of Professor Agassiz, in the “Poissons Fossiles,” 
of the Bristol species, except that the transverse section is more decidedly oval and 
is not so sharply produced anteriorly. This character, however, is not of sufficient 
importance to form a specific difference, but, not having had an opportunity to 
examine the Belgian species, I do not feel justified in placing it definitely with 
Ctenacanthus major, Ag. 
Formation and locality : Mountain Limestone, Bristol. 
Ex coll. 1. Earl of Enniskillen; 2. Bristol Museum. 
Ctenacanthus tenuistriatus, Agass. 
(Pl. XLIIL, figs. 1, 2.) 
Ctenacanthus tenuistriatus—L. Agassiz, 1837. ‘“ Poiss, Foss.,” Vol. III.,p.11,pl. ii., figs. 7-11. 
* 55 P. deM. Grey Egerton, 1839. “Catalogue of Fossil, Fish.” 
C. G. Giebel, 1848, “ Fauna der Vorwelt,” Bd.I., Abth., ITT., p. 308. 
5 3 H. G. Bronn, 1848. “‘Nomencel. PalJeont.,” p. 355. 
7 5 J. Morris, 1854. “Cat. British Foss.,” p. 323. 
oH F. J. Pictet, 1854. ‘“Traite de Paleont.,” Vol. II., p. 290. 
Morris and Roberts, 1862. “ Quar.Jour., Geol. Soc.,” Vol. X VIIL., p. 100. 
P.deM. Grey Egerton, 1869. 
Young & Armstrong; 1871. 
Armstrong, Young, 
and Robertson, \ Hous 
J.J. Bigsby, 1878. 
L. G. de Koninck, 1878. 
“ Catal. Type Specimens of Fossil Fishes,” p.5. 
“Transactions Geological Society, Glasgow,” 
Vol. IIL, Supplement, p. 70. 
. “Catalogue of the West. Scot. Fossils,” p. 61. 
“Thesaur. Devon.-Carb.,” p. 351. 
“ Annales de Musée Royal d'histoire naturelle 
de Belgique,” Vol. II., p. 67, pi. vii, fig. 2. 
Spine, of moderate size, a perfect specimen being fourteen to fifteen inches in 
length, greatest breadth two inches. The specimens described by Prof. Agassiz 
were very imperfect, and afforded insufficient material for a complete description. 
The lower portion of the spine is almost straight, with a very slight curvature back- 
wards ; base rounded; the upper part, about one-fourth the length of the whole, 
contracts rapidly in diameter, posterior surface deeply curved, and terminating 
with an acutely pointed apex. It is this portion of the spine which is represented 
in the “Poissons Fessiles,’ Vol IIL, pl. iii, fig. 7. The lateral surfaces are compressed 
and covered with minute longitudinal striz, with intervening grooves, about the 
same width as the ridges. The ridges increase in number towards the base, by 
bifurcation. Each ridge is characterized by minute transverse foldings of the 
surface. This species differs considerably from C. major, Ag., in the paucity of the 
ridges, not only are the longitudinal ridges more slender than those of C. major, 
but those towards the posterior portion of the surface are considerably finer and 
smaller than those on the anterior surface. The anterior border is well rounded, 
TRANS, ROY. DUB. SOC., N.S, VOL. I. 4 3K 
