368 On the Fossil Fishes of the Carboniferous Inmestone Series of Great Britain. 
of the fish. The line separating the two parts extends obliquely from the convex 
to the concave surface, with apparently the contrary direction usually observed on 
fish-spines. The inner or concave margin, which was probably the posterior one, 
was less deeply implanted in the integuments than the anterior one. The curvature 
of the anterior margin forms the are of a circle exceeding one-third its circumference ; 
its greatest diameter is ‘9 inch at the junction of the base with the exposed surface. 
The base is large and expanded, more or less bilobate, much compressed. The 
exposed portion gradually tapers towards the puint, an1 if perfect would probably 
terminate acutely. The lateral and anterior surfaces are covered by numerous 
rounded longitudinal ridges, “less than their own diameter apart, dilated into 
rounded, smooth, bubble-like tubercles, which are nearly twice their diameter apart ; 
some of the tubercles occasionly flattened and transversely oblong ; the narrow 
sulci between the ridges have usually two or three obscure longitudinal strize ; on 
the posterior edge are two irregular alternating rows of obtusely pointed tubercles, 
finely stellated by radiating strive at base, and about one line in diameter.” | 
A large and massive spine, Physonemus gigas, N. and W., a foot or more mn 
length, and two inches in diameter has been described by Messrs. Newberry and 
Worthen (“ Geol. Survey of Illinois,” Vol. VI., p. 373. pl. ii, fig. 1). It 1s from the 
Burlington Limestone, and very closely related to Physonenus arcuatus, M‘Coy ; its 
large size and an obliquely conical form of the stellate posterior tubercles being 
the only differences. The authors named above, consider that the curvature of the 
spines of this genus is reversed, the concave surface being the anterior one and 
vice versa ; the correctness of this supposition is very doubtful and it appears most 
probable that the spine is bent backwards in the ordinary manner, the denticles are 
extended along the concave surface, and there is a decided groove between the two 
rows in some of the specimens. The diverse obliquity of the line of demarcation 
_ between the basal and upper portions of the spine, may easily be accounted for by 
the form of the spine, and is such as would naturally accrue from its great 
curvature. 
Formation and locality : Mountain Limestone, Armagh. 
Ex coll, Earl of Enniskillen. 
Physonemus subteres, Agass. MS. 
(2, XSU\VIOL,, inke, 1193.) 
Physonemus subteres—L. Agassiz, 1837. “Rech. sur]. Poiss. Foss.,” Vol. III., p. 176, indet. 
” » J. E. Portlock, 1843, «Rept. Geol. Londonderry, &e.,” p. 461. 
” » ©. G. Giebel, 1848. “Fauna der Vorwelt,” Vol. L, pt. 3, p. 310. 
” ” H. G. Bronn, 1848. ‘‘Nomencl. Paleont.,” p, 972. 
” ” 9 1849. “ Enumerator Palont.,” p. 653. 
D »” J. Morris, 1854. “Catal. Brit. Foss.,” p, 338. 
” » F. J. Pictet, 1854. “Traité de Paléont.,” Vol. II., p. 291. 
” »  F. M’Coy, 1855. “Brit. Paleoz, Foss.,” p. 638, pl. 3, L, fig. 30. 
” ” Morris & Roberts, 1862. “Quart. Journ. Geol. Soc.” Vol. XVIIL., p. 101. 
” » J. J. Bigsby, 1878. “Thesaurus, Devonico Carb.,” p. 363. 
