480 On the Foss:i Fishes of the Carboniferous Limestone Series of Great Britain. 
has a quadrate form. The Yorkshire genus, Dimyleus, appears to occupy an 
intermediate position between those of Pinacodus and Mylax, both in form and 
structure. | 
Formation and locality : Mountain Limestone, ANTENA 
Hx. coll. Kar] of Enniskillen. 
Genus.—Mylacodus, Agass. MSS. 
Mylacodus—L. Agassiz, 1859. MSS., Enniskillen Collection. 
Palatal teeth, outline subquadrate, medium size. Crown; longitudinally, 
slightly convex; transversely, central area convex; broad lateral depressions 
with a shghtly raised lateral border. Coronal surface thickly enamelled, punctate 
or rugose. Anterior and posterior margins convex, lateral ones nearly straight ; 
antero- and postero-lateral angles rounded. Base thick, transversely rounded, 
deepest in middle, extends to, or a little beyond, the lateral margin of the crown, 
anteriorly retreats slightly and has a compensating prominence posteriorly. 
Mylacodus quadratus., Agass. MSS. 
(Bl LVIM., figs: 27, 28:2) 
Mylacodus quadratus—L. Agassiz, 1859. MSS., Enniskillen Coll. 
5 5 Morris and Roberts, 1862. <‘‘Quart. Journ. Geol. Soc.,” Vol. XVIII., p. 101. 
5 a Enniskillen, 1869. ‘Catal. Type Specimens,” p. 6. 
% 55 J.J. Bigsby, 1878. ‘Thesaurus Devonico-Carb.,” p. 359. 
Teeth : subquadrate, length °75 of an inch ; breadth -7 to -8 of aninch. Crown 
more or less horizontal, longitudinally and transversely convex in middle area, 
with a broad shallow depression on each side, and a slightly raised lateral border. 
Anterior area generally considerably worn by attrition during mastication. In- 
stances occur in which the whole central part of the crown has been worn 
away. Coronal surface thickly enamelled, covered with an irregular arrange- 
ment of pittings. Anterior margin convex, laterally almost straight, with 
tendency to convexity; enamelled edge of crown in some instances serrated ; pos- 
terior margin convex, slightly broader than the anterior one ; antero- and postero- 
lateral angles all obtusely rounded. Base °3 of an inch thick at the back of the 
tooth ; -2 of an inch in front; longitudinally straight ; transversely rounded, thick 
in the middle, thinning out towards each side, where the base projects slightly — 
beyond.the coronal margin. In front the base retreats from the enamelled surface 
with a slight concavity. Behind, on the contrary, the base projects slightly beyond 
the enamelled surface. 
This species is tolerably common at Armagh. The specimens vary in size from 
the one described to palates not more than a quarter of an inch in diameter. They 
also offer some variation in form, Examples occur in which the tranverse diameter 
