362 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 
hollow, basal portion forming a deep sulcus from which an internal cavity extends 
upwards towards the superior extremity. Each latero-posterior angle is armed 
with a row of recurved broadly-implanted, rapidly-tapering, finely-pointed teeth 
rather widely separated, especially on that portion nearest the basal sulcus. 
A second specimen, representative of others, is almost straight, shorter, and 
wider in proportion to its length than those just described. In other respects it is 
very similar. It possibly occupied a position in front of the second dorsal fin, 
whilst the longer and more curved specimens may have been similarly placed before 
the first dorsal fin, as in the existing Acanthias. 
The description of Homacanthus given by Prof. M‘Coy was from a very imperfect 
but at the time unique specimen. There is in the Enniskillen collection a consider 
able series, which has led to modifications of, and additions to, the description given 
by Professor M‘Coy. 
Formation and locality : Mountain Limestone, Armagh. 
Ex coll. Karl of Enniskillen. 
Homacanthus macrddus, M‘Coy. 
(Pl. XLVIIL, fig. 14.) 
Homacanthus macrodus—F. M‘Coy, 1848. “Ann. & Mag. Nat. Hist.,” 2ndser., Vol. 1I., p. 115. 
5 x J. Morris, 1854. “Catal. Brit. Foss.,” p. 329. 
5 6 F. J. Pictet, 1854. “Traité de Paléont.,” Vol. I1., p. 288. 
9 . F. M‘Coy, 1855. “Brit. Paleoz. Foss.,” p. 632, pl. 3 K, fig. 20. 
a 5 Morris & Roberts, 1862. “Quart. Journ. Geol. Soc.,” Vol. XVIIL, p. 100. 
» i J. J. Bigsby, 1878. “Thesaurus Devon.-Carb.,” p. 357. 
“Spine, about eight lines long and two lines wide at the base, slightly arched and 
tapering to a point, section compressed, trigonal, anterior face formed by a narrow 
rounded keel ; posterior concave face bounded on each side by a large rounded ridge, 
between which and the anterior keel there is on each side a still smaller rounded 
longitudinal ridge ; the two posterior ridges on each side dichotomize near the 
base of the two intervening spaces, the anterior 1s rather wider and the posterior 
rather narrower than the ridges, which they separate; they are concave and very 
finely striated longitudinally ; posterior face with twelve or fourteen very large com- 
pressed falcate teeth, alternating in two rows, the alternating bases touching, keeled on 
their convex edge,their length nearly equalling thewidth of the side of the ray at their 
base.” 
This spine is distinguished from the last, H. microdus, M‘Ooy, by the absence of 
strie in the sulci between the ridges, in the different arrangement of the longi- 
tudinal ridges, and the large falcate teeth which extend along the posterior angles. 
Thelatter characteristic and the lessnumerous ridges, distinguish it from 1. arewatus 
Ag., of the Old Red Sandstone. 
Formation and locality: Mountain Limestone, Armagh. 
Ex coll. Woodwardian Museum, Cambridge. 
