On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 517 
-Petalorbynchus psittacinus—Enniskillen, 1869. ‘Catalogue Type, Spec.,” p. 7. 
Petalodus Young & Armstrong, 1871. “Trans. Geol, Soc., Glasgow,” Vol. IIL, 
Supt., p. 74. 
3 sagittatus— 0 1871. “Trans. Geol. Soc., Glasgow,” Vol. ITI., 
Supt., p. 75. 
Armstrong, Young, o 
and Robertson, ; \ LO0@, 
J. J. Bigsby, 1878. ‘Thesaurus Devon.-Carb.,” p. 361. 
J. W. Davis, 1881. “Rep. Brit. Assoc.,” p. 646. 
Petalorhynchus psittacinus | “Catal. of West Scot. Foss.,” p. 62. 
” 9) 
2? LP) 
Teeth, medium size, consisting of, at least, three vertical and five transverse 
rows of teeth in each jaw; form much varied in different parts of the mouth 
according to situation. Crown generally longer and narrower in central row, and 
broader and shorter laterally ; spatulate. Base very long in primary horizontal 
row, diminishing in the teeth occupying second and succeeding rows; length of 
average specimen, 1°0 to 1°5 inch; breadth of crown, 6 to °8 of an inch; length 
of crown, anteriorly, one-third that of base ; posteriorly, slightly longer than its 
breadth. Crown acutely angular, with a sharp cutting edge, poimted in the 
middle, resembling the beak of a parrot; anterior surface laterally convex ; 
median portion, from the point downwards, forming a prominent ridge, laterally 
expanded and depressed with thin circular margins. Anterior ridge separating 
crown from base, extends’ sigmoidally across the surface ; ornamented with four 
or five folds of ganoine extending slightly upwards on each side from the central 
ridge of the tooth, and recurved towards the lateral margins of the crown, forming 
with them an acutely-pointed decurrent angle. Posterior surface deeply concave, 
spoon-shaped, nearly twice the length of the anterior surface; posterior ridge 
covered with an equal number of enamelled folds, continuous with those on the 
anterior surface ; from the lateral margins they curve downwards towards the base, 
then recurving sigmoidally meet and unite on the median line. Root, like the 
crown, varies in form in accordance with the position occupied in the arrangement 
of the teeth, Ina typical example from the primary row of teeth, the root is 
twice as long as the anterior face of the crown, and from the point of its connexion 
with the crown gradually diminishes in diameter to the bottom, On the anterior 
surface, the central coronal ridge is continued downwards to the base, at first 
expanding in width for about one-third the length of the root, afterwards gradually 
contracting. On either side the ridge is a deep sulcus which extends to the lateral 
margins. Posteriorly, the root is depressed medially, with a slight ridge on each 
side, from which the surface slopes to the lateral margins, termination of base 
obtusely angular. The coronal surface is smooth, or very slightly punctate, 
enamelled, and highly polished: cutting edge of crown in most cases smooth, 
occasionally very slightly imbricated. The crown is frequently worn along the 
edge, on one side only, in such a manner that the effect could only he produced 
by the grinding action of an opposing tooth, which served at the same time to 
