REPORT ON FOSSIL FISHES. 57 
posterior-inferior angle of the operculum; and again, turning from the 
posterior-superior to the anterior-inferior angle of the interoperculum, divides 
each plate into two diagonal halves ; behind this line the ornamentation is in 
each case tubercular, while in front it consists of sub-parallel anastomosing 
ridges, running mainly in a horizontal direction. In front of these two plates 
is the interoperculum, shaped as in Chezrodus, but here seen only from its inner 
aspect ; a small narrow additional plate seems to be intercalcated between it 
and the upper part of the anterior margin of the operculum. The orbit is 
placed pretty high up on the head, and right over the middle of the mouth; a 
narrow sickle-shaped suborbital is seen bounding it behind. 
The mandible is short, deep, and stout, though pointed, beak-like, in front ; 
where the upper margin of its dentary element is seen, it is thin and edentulous, 
The external surface of the mandible is shown in the second and larger speci- 
men, both dentary and angular elements being sculptured with coarse flattened 
ruge, sometimes anastomosing and interrupted, subparallel, and running 
obliquely from above and behind downwards and forwards. The impression of 
the outer aspect of the maxilla is seen in the counterpart of the same specimen ; 
it is of the triangular shape seen in Lurynotus and Cheirodus, and is ornamented 
by rugee similar in character to those of the mandible, but parallel to the poste- 
rior margin, and nearly vertical to the inferior or oral one. Its free or oral 
margin is sharp and edentulous as in Cheirodus, but probably enough, as in that. 
genus, there was a supra-marginal band of tooth tubercles in the inner surface. 
In the smaller specimen an excellent view is afforded of the inner or oral 
aspect of the pterygo-quadrate apparatus, which is conformed exactly as in 
Cheirodus. The pterygoid element, seen also isolated in the larger example, is 
somewhat oval in shape, convex below and internally; its internal surface 
shows a narrow band of small shining tubercles, while the lower margin displays 
two strong ridges, converging behind, and anteriorly carrying each a row of 
tooth tubercles, which are covered with a brilliant coating of enamel, and are 
more closely set than in Cheirodus granulosus. 
Of the bones of the shoulder girdle the only one visible is the clavicle, 
whose form corresponds with that in Cheirodus and other Platysomid fishes. 
The scales (fig. 19) are high and narrow, indeed remarkable for the narrowness 
of the exposed area, which is covered with a peculiar coarse tuberculo-corrugate 
ornamentation, which forms prominent serrations at the hinder margin. The 
articular spine is well marked, as is also the receiving fossette of the internal 
surface, but the vertical keel or so-called “scale rib” is broad, and only very 
slightly prominent. 
The dorsal fin, as seen in the smaller specimen (fig. 17), commences behind 
the summit of the gently rounded line of the back; unfortunately the specimen is 
so cut off that the free margin of the fin is absent, though a considerable 
