472 On the Fossil Fishes of the Carboniferous Limestone Series ef Great Britam. 
lateral angles, and posteriorly the base extends beyond the coronal surface, appar- 
ently to give support to a succeeding tooth. This is notso in Pleurogomphus ; the 
distinguishing characteristic of the genus is in the division of the posterior area 
into three parts by sulci, and in this it mainly differs from Mesogomphus in which 
there is only one suture, and that a median one. 
Pleurogomphus auriculatus, Agass. MSS. 
(el, IWINUL,, tes, 1S, Why, LBs) 
Pleurogomphus auriculatus—L. Agassiz, 1859. MSS. Enniskillen Coll. 
5 Morris and Roberts, 1862. “« Quart. Jour. Geol. Soc.,” Vol. X VITI., p. 101. 
a Enniskillen, 1869. ‘Catal. Type Spec.,” p. 7. 
. . J. J. Bigsby, 1878. ‘Thesaurus Dey.-Carb.,” p. 363. 
Teeth, sub-quadrate in outline, rounded at the anterior angles ; length, along 
median axis, ‘75 of an inch; breadth, same as length. Crown, concave ; concavity 
increased at the anterior portion by attrition ; lateral borders very slightly raised. 
Posterior third of the coronal surface is obliquely depressed, and on each of the 
latero-posterior portions there is a circular sulcus or suture, very similar to the 
median one vf Mesogomphus, except that in this genus there are two sutures, 
cutting off or separating portions of the posterior surface at each corner, and leaving 
the central portion connected with the crown, The sutures divide the posterior 
margin into three equal parts, and extending longitudinally for a distance of about 
‘2, of an inch, they curve in each case towards the lateral margins, to which they 
approximate at ‘1 of an inch from the postero-lateral angle. The surface of the 
separated portions 1s convex in front, the back portion receding. ‘The whole of the 
coronal surface is punctate, and where not too much worn is coated with enamel. 
On the anterior portion, where the enamel has quite disappeared, the punctate 
character of the surface is still retained. Anterior margin broadly circular ; 
lateral margins straight. The enamelled surface forming the anterior margin 
projects beyond the base. Posteriorly the margin is straight, except that each 
postero-lateral border is produced, and forms an acutely-projecting angle. Base 
thick, strong; longitudinally striated and concave; transversely it is deeply 
convex, thinning towards each lateral margin, and extending slightly beyond the 
crown. The posterior margin of the base conforms generally to that of the crown, 
but like the anterior, does not extend so far as the coronal surface. 
Formation and locality : Carboniferous Limestone, Armagh ; a unique example. 
Ex coll, Earl of Enniskillen. ; 
