320 
CROSSOPTEKYGrII. 
below the eye are conspicuous; the dentigerous maxilla bounds 
these below, and exhibits a small (apparently jugal) plate behind its 
posterior expansion. The latter element extends far backwards, 
and immediately above it is a very large cheek-plate covering the 
whole of the space between the posterior suborbitals, the cranial 
roof, and the preoperculum. On the roof of the mouth there is a 
well-ossified parasphenoid, meeting in front a pair of vomers, each 
of which bears a powerful tooth ; and there are some traces of an 
inward palatal extension both of the maxillae and premaxillae. 
The mandible is very complex and seems to possess a distinctly 
ossified articular element. The dentarv bone is relatively deep and 
thick at the symphysis, tapering backwards, and bears a series of 
small teeth, with a single large laniary in front. The lower 
border is bounded by a series of three or four, plate-like, lenticular 
bones, of which the hindermost seems to correspond to the angular, 
while the others are conveniently termed infradentaries. A thin 
splenial lamina forms the inner wall of the ramus, and between this 
and the dentary is arranged a series of about three or four very 
stout lenticular bones, each of which bears a laniary tooth. 
A deep and narrow preoperculum is observed behind the cheek- 
plates, while the operculum and suboperculum are well developed; 
there is, however, no representative of an interoperculum. Below 
the suboperculum a long narrow plate forms the hinder element of 
the series of lateral jugulars on each side ; and a pair of very large 
principal jugular plates, with or without a small anterior azygous 
element, occupies the whole of the space between these series. 
The cranial roof is bordered behind by three small supratemporal 
plates, one median and a pair lateral; but there appear to be no 
large scales on the posterior margin of the pectoral arch. Behind 
this, so far as known, the squamation is always continuous; and 
the only enlargement of the scales is observed occasionally at the 
bases of the fins and in the anal region. There are rarely indi¬ 
cations of a peg-and-socket articulation of the scales, although the 
inner rib is usually conspicuous in those that are rhomboidal, while, 
except in the Holoptychiidse, this rib is represented by a median boss 
in the more deeply overlapping scales of cycloidal form. In one 
genus ( Megalichthys ) the scale-arrangement proves the anus to have 
been placed at some distance in advance of the anal fin, and not 
quite in the mesial line. 
A lateral line arising immediately above the operculum traverses 
a longitudinal series of scales as far as an undetermined point on the 
caudal pedicle ; and, at least in the Holoptychiidse, there is another 
similar line arising from the jugular plates of either side. In the 
