402 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 
Rhamphodus dispar, Davis. 
(Al, IOIL, ies, 17, Wao) 
Teeth, Length from the pointed crest of the crown to the left lateral extremity 
is 1‘l inch: opposite side is ‘7 inch. ‘The crown is produced and curved towards 
the posterior face, presenting something like the appearance of a bird’s beak. 
Lateral surfaces compressed, their junction constituting an obtuse median ridge. 
There are no minor lateral prominences. ‘The surface is uniformly covered with 
minute pustulate projections. At a distance of °3 inch from the apex, the crown 
bifurcates rectilinearly with an obtusely-rounded angle, forming two lateral exten- 
sions of unequal length as stated above. The lateral extremities are thin, somewhat 
angular, with a well defined ridge extending alongthe posterior surface. . The shorter 
one terminates in a projecting rounded boss: the longer in a backwardly-curved 
obtusely-pointed extremity. Anterior surface thin, partly hidden by matrix. 
Posterior surface, angular and deeply grooved vertically, as though by rubbing 
against an opposing tooth. Lateral extremities below the bifurcation, are about ‘1 
of an inch in thickness, being one-half the breadth. The basal portion of the tooth 
is only visible in the centrally divided portion, and is not large. 
Its nearest affinity seems to be with Helodus, but it differs from that genus so 
materially in the pointed recurved character of the crown, in its pyramidally 
acuminate form, and the deeply divided base, that it is extremely doubtful whether it 
can have occupied an equivalent position to the teeth of Helodus. It also bears a 
superficial resemblance to an American form from the St. Louis limestone which was 
described by Dr. Leidy under the name of Chomatodus venustus (‘ Trans. Am. Phil. 
Soc. Philadel.,” Vol. XI., pl. v., figs. 19-21). The species was afterwards included 
in the genus Venustodus with the specific name Leidyi, by Messrs. St. John and 
Worthen (“ Paleon. of Ill,” Vol. VI., p. 350, pl. ix., figs. 1-4). The teeth included 
under this definition are of two kinds, one presenting a similar angular form with 
pointed crest, to those described above, the second form is smaller and only slightly 
arched in outline. The first form only exhibits any relationship with the Armagh 
specimen and it is very probable that itis merely accidental: Venustodus letdyi differs 
from the tooth now described in having an acuminate apex to the crown without 
curvature, in the lateral extensions of the crown being equal in leneth, and in the 
lateral expansions being occupied by a variable number, between ten and eighteen, 
of delicate, though well defined, denticulations : the crown is also encircled by a 
continuous belt of coronal folds, and the base forms a relatively narrow plate, nearly 
co-extensive with that of the crown. 
Formation and locality : Mountain Limestone, Armagh. 
Hz coll, Earl of Enniskillen. 
