446 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 
Laterally the margins are nearly straight—the median one converging obliquely 
towards the posterior margin, which is comparatively narrow and convoluted 
inwards. Base not well defined. 
This species is defined by well-marked differences from Pacilodus jonesw described 
above, and P. obliquus, M‘Coy (Brit. Paleeoz. Foss., p. 640, pl. 3 L., fig. 5). The 
latter is characterized by three strongly convoluted, very prominent, nearly equi- 
distant ridges, with intermediate concavities, the latter crossed by irregular 
transverse wrinkles, which do not generally extend over the surface of the ridges. 
P. jonesii has two sub-parallel ridges, with one deep intermediate depression, and. 
the whole surface is divided by transverse wrinkles or folds. The species described 
above has only one important median ridge, larger and broader, in proportion to the 
size of the tooth, than those of either P. jonesii or P. obliquus, and the transverse 
folds extend only over the ridge, and do not traverse the depressed portions of the 
surface. In P. gibbvsus the depressed postero-lateral portion is much constricted 
in area between the anterior and posterior margins—a character which does not 
obtain in the others. 
Formation and locality : Mountain Limestone, Armagh. 
Ez. coll, Ear] of Enniskillen. 
Genus.—Tomodus, Agass. (MSS.) 
Palatal teeth, large, thick, massive, triangular or sub-rhomboidal in outline, con- 
volute. Crown, surface antero-posteriorly semi-rotund, laterally convex, thickly 
coated with enamel or dentine, punctate. Anteriorly more or less pointed, 
laterally diverging and forming a broad posterior margin. Base, thick, osseous. 
This genus differs from all the other Cochliodont teeth in its thick massive and 
triangular characters. The postero-lateral margin has evidently been connected 
with a second tooth or has formed the median line over the jaw, in which case 
there would probably be only two teeth to each jaw, one on each ramus. The 
latero-posterior margin is thinner and does not present the appearance of having 
been attached to another tooth. 
Tomodus convexus, Agass. (MSS.) 
(Pl. LV., figs. 15-18.) 
Tomodus convexus — L. Agassiz, 1859. “ MSS. Enniskillen Coll.” 
* os Morris & Roberts, 1862. ‘ Quart. Journ. Geol. Soc.” Vol. XVIIL., p. 101. 
Cochlivdus ss R. Owen, 1867. “ Geol. Mag.” Vol. IV., p. 62, pl. 4, figs. 2-5. 
Tomodus 5 Enniskillen, 1869. “ Catal. Types Foss. Fishes,” p. 8. 
Armstrong, Young FR GBR ” 5 
e : peer a 1876. “Catal. W. Scot. Foss.” p. 63. 
4 J. J. Bigsby, 1878. ‘‘ Thesaurus Devonico-Carb,” p. 365. 
