On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 461 
exhibits the same surface markings in unworn specimens as well as the smooth and 
punctate appearance where the rugose markings have been removed by trituration. 
The rugosities in this form extend across the short diameter of the tooth, and if, 
as appears probable, this form was placed laterally alongside the larger specimens, 
the rugose markings of each would lie parallel in the same direction. 
A reference to the figures on Plates LVI. and LVIT. will illustrate better than any 
amount of description the varied forms assumed by these teeth. The outline most 
commonly observed is the one shown in Pl. LVL, fig. 1, a magnificent specimen 
from the collection of Lord Enniskillen. The concave surface is the posterior 
part of the tooth and was probably joined to another tooth; the anterior margin 
is convex, the right side, which is the median line in the mouth, is straight, whilst 
the opposite one expands obliquely backwards. In the accompanying figure. 1 b, 
representing a section of the tooth, the crown is represented -2 of an inch in 
depth, whilst the root varies from -4 to ‘6 in the central part, the lateral portions 
being at the straight side ‘8 of an inch, and on the oblique or external side it is 
I‘Linchin depth. Prof. de Koninck (Fauna du Caleaire Carbonifére de la Belgique, 
p. 42) has ventured an opinion that the teeth were arranged in three rows of four 
teeth, each containing two of the broad teeth spoken of above, and on each side a 
narrow tooth (the P. canaliculatus of M‘Coy). After very carefully studying 
the large collection of specimens in the Enniskillen and other collections, it 
appears very probable that a modification of this arrangement may have been the 
one which existed. Prof. de Koninck remarks, “Je ferai remarquer que cette 
derniere disposition n’est nullement hvpothetique comme ou pourrait le croire ; 
je lai observée sur une specimen de la collection de M. Neilson de Glasgow et 
dont les trois dents conservées en place sont exactment reproduites par le dessin. 
Tl est done probable que pendent la vie de Vanimal ces dents étaient plus ou 
moins mobiles et séparées les unes des autres par une légere couche de matiére 
cartilagineuse ou fibreuse.” 
The form of the large teeth serves to confirm the opinions stated above, because 
in every instance either the right or left lateral margin is straight, proving that 
whilst the obliquely inclined margin conformed to the outer shape of the jaw, the 
straight side was adapted to fit the straight edge of the tooth on the oppesite ramus 
of the jaw. In addition to the tooth shewn on Pl. LVI, fig. 1, a less common 
form is represented on Pl. LVIL, fig. 7, the diameter of which is twice or three 
times greater between the antero-posterior margins than between the lateral ones, 
and as stated the rugosities when present lie across the surface parallel with the 
shorter diameter. The teeth are generally slightly curved, concave on the inner 
margin, convex on the outer one; the outer postero-lateral angle is produced 
acutely as in the larger teeth, and served to support the antero-lateral extremity of 
the succeeding tooth. Examples of this form occupied the lateral extremities of 
each jaw. A third somewhat persistent form is représented on P]. LVIL., fig. 3. 
Tt is similar to the last, except that its anterior margin is much contracted in 
