ASPlDORHYNCHIDiE. 
417 
some indications of a short supramaxiLla above its hinder end. The 
premaxilla is also much elongated, with relatively large and spaced 
teeth posteriorly diminishing to minute teeth forwards ; it is fused 
with the ethmoidal region, but does not meet its fellow of the 
opposite side in front, the groove between this pair of bones being 
continued for some distance along the base of the rostrum. Two 
relatively large plates of the suborbital series occupy the greater 
portion of the cheek behind the orbit; but the upper plate, as also 
sometimes the superior end of the lower plate, is separated from 
the preoperculum by a third element which is truncated above and 
acuminate below. There are also small cheek-plates surrounding the 
narial opening immediately in advance of the orbit; but the circum- 
orbitals are insignificant and apparently do not form a continuous 
ring. The sclerotic is ossified. The dentary is much the largest 
element in the mandible and bears a single series of teeth on 
its oral border. It meets its fellow of the opposite side at the 
symphysis, and articulates in front with an azygous, bilaterally- 
symmetrical presymphysial bone. Posteriorly there is a small 
angular plate exposed on the outer face of the ramus; but the 
coronoid has not hitherto been observed. The splenial is a very 
thin lamina, excavated on its hinder border and bearing minute 
teeth. 
On the branchial arches the calcified supports for the gill-filaments 
are always conspicuous. The opercular apparatus is complete, and 
there is a long series of branchiostegal rays ; but a gular plate has 
not hitherto been observed. 
The vertebral centra, so far as the present writer has observed 
them, are always in the form of delicate rings, each bearing its own 
arch. The ribs are very short and thin. In the abdominal region 
the neural spines appear to be separate from their supporting arches, 
though this is not quite certain ; in the caudal region, both haemal 
and neural spines are fused with their arches, and the latter with 
their respective centra. As might be expected from the stout pro¬ 
portions of the rays, the supports of the dorsal and anal fins are 
especially robust; and they are shown to be more numerous than 
the vertebral segments beneath them. 
The scales are all thick and rhombic, strengthened by a slight 
internal median rib, and those of the flank united by a large 
peg-and-socket articulation. The lateral line pierces each scale it 
traverses. 
2 E 
PART III. 
