﻿44 GANOID FISHES OF THE CARBONIFEROUS FORMATION. 



shaped, though as usual it is broader behind than in front. The prseoperculurn {p. op.) 

 is unusually narrow, its upper limb is very obliquely placed on the side of the head, and is 

 about twice the length of the lower one. The maxilla is also rather narrow, the depth of 

 its posterior broad portion being contained about four times in the entire length of the 

 bone. The mandible is stout and nearly straight, though slightly curved upwards at its 

 extremity ; the depth of the dentary portion {d) is contained about five times in the entire 

 length of the jaw ; distinct articular, angular, and splenial elements may also be made out 

 in various specimens. The branchiostegal rays {dr.) are at least thirteen on each side, the 

 anterior of each lateral series being broader than the others, and having between them, 

 in front, an azygous lozenge-shaped plate. Nothing can exceed the beauty of the sculpture 

 of the external surfaces of these facial bones, which consists of delicate yet sharply defined, 

 nearly parallel, and slightly wavy, branching and anastomosing ridges, whose general 

 direction is indicated in PI. Ill, fig. 3. Nowhere on the head have I seen a tubercular 

 ornament, the surface of the cranial roof-bones being everywhere ornamented by similar 

 delicate ridges or raised striae, which run for the most part in an antero-posterior 

 direction. 



The teeth are difficult of detection, being almost always concealed by the hard 

 intractable ironstone matrix, usually very pyritous, but in one instance I succeeded in 

 showing the dentition of the lower jaw by corroding away the bony matter with nitric 

 acid, and making a squeeze in modelling wax from the preparation thus obtained, the 

 same as that from which the representation of the facial bones given in Plate III, fig. 3, 

 was taken. This shows a row of sharp, incurved, conical laniary teeth (PI. Ill, fig. 4), 

 each about ^th inch long (in a jaw of i%ths inch in depth at its stoutest part, and more 

 than 11 inch in length) and rather less than their own length apart ; they are thus rather 

 small and closely set. Outside there is a series of much smaller teeth, one half the size 

 of the inner series and less. In the same preparation, teeth are also seen in the most 

 posterior part of the edge of the maxilla, though those of the rest of that bone are 

 concealed. 



The post-temporal is of the usual form, the supra-clavicular is broad ; both are shown, 

 though rather crushed, in the specimens represented in PI. Ill, figs. 1 and 2. In fig. 1 

 there is a good view of the clavicle and interclavicular seen from their inner surfaces ; its 

 last-named element is in this instance transversely fractured right through its middle. In 

 the fish represented in fig. 2 there is distinct evidence of the radial elements supporting 

 the rays of the pectoral fin • these have been already described at p. 24. 



The fins are large, though not so "immense" as Agassiz has described them, and an 

 examination of the original specimen shows that they are greatly exaggerated by his artist 

 in the figure of the fish given in the ' Poissons Fossiles,' Atlas, vol. 2, tab. 4 b, fig. 3. The 

 pectorals are broad and acuminate (PI. Ill, fig. 2), the ventrals, like those of Cheirolepis, 

 are remarkable for the length of their base of origin, this equalling 1^ inch in the same 

 specimen, which would, if entire, measure 10^ inches from the tip of the snout to the 



