On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 447 
Palatal teeth of two sizes with distinctive characters. Larger teeth triangular, 
length antero-lateral margin 1:25 inch; postero-lateral margin 1:5 inch, and 
posterior margin 1:1 inch. Crown, antero-posteriorly deeply convex or semi- 
globose ; laterally convex, even and smooth except where a sulcus extends across 
the postero-lateral angle of the tooth ; thickly enamelled and minutely and closely 
punctate. Anteriorly the tooth is pointed and convoluted, the lateral margins 
diverge posteriorly ; posterior margin straight or slightly convex ; postero-lateral 
angle produced with a somewhat sinuous flexure. Base ‘3 inch thick in centre, 
thins out slightly towards both the anterior and posterior margins. Smaller teeth, 
oblong or sub-rhomboidal in outline. The surface is laterally concave, the margins 
being raised and forming a ridge along each side. 
The specimen from the Carboniferous limestone of Bristol referred to by Prof. 
Owen (Geol. Mag. Vol. IV., p. 62), as Tomodus converus, Ag., which forms part of 
the collection at the Woodwardian Museum, Cambridge, presents every appearance 
of being, so far as the teeth are concerned, a defective and much broken specimen 
of Cochliodus contortus, Ag. ; as remarked by Prof. Owen it is the most completely 
preserved specimen of a mandible of a Cochliodont known. It will be treated with 
greater detail when speaking of Cochliodus in this memoir. 
Formation and locality : Mountain Limestone, Bristol. 
Ex coll. Ear) of Enniskillen. 
Genus.—Xystrodus, Agass., MSS. 
Syn. Cochliodus (pars.)—Agassiz, 1838. ‘Rech. Poiss. Foss.,” Vol. IIL, p. 174. 
»  Pecilodus ,, % 1838. s yp 5 Ao) ie so 
Palatal teeth more or less triangular in outline, medium or small size, slightly 
convoluted and acutely pointed anteriorly: antero-lateral margin forms a 
convex articulating ridge raised higher than the general surface of the crown, 
the remainder of which is depressed and concave, expanding in breadth posteriorly. 
Posterior margin sigmoidally convex forming an acute angle with the postero- 
lateral margin. Surface enamelled, punctate or pustulate—the puncta sometimes 
arranged so as to fall into regular lines. Base thick and strong. 
TRANS, ROY. DUB. SOC., NS., VOL, 1. 4A 
