1870. ] HANCOCK AND HOWSE—DORYPTERUS HOFFMANNI. 633 
shaped areas. This upper series of ridges forms a line which ex- 
tends from the nape, a little above the commencement of the lozenge- 
shaped areas, and, passing backward parallel to them and about mid- 
way between them and the dorsal margin, terminates immediately 
behind the anterior elongated portion of the dorsal fin. This line of 
ridges resembles the upper line of mucus-tubes in Polypterus (‘ Pois- 
sons Fossiles,’ t. 1. pt. 2. p. 50) and in Dapedius punctatus (ibid. t. il. 
p- 192, pl. 25a); and, indeed, in the latter, which in form closely 
resembles Dorypterus, this upper or second lateral line, according to 
Agassiz, holds relatively exactly the same position. 
The marginal hour-glass-shaped plates have their sides abrupt and 
slightly elevated into ridges. A similar ridge passes along the centre ; 
and the most contracted part of the plate is thickened or elevated, 
the ends becoming depressed and thin. These peculiar plates, we 
have said, form a portion of a marginal series (fig. 1, /) that reaches 
to the root of the tail. Behind the anterior or elevated division of 
the dorsal fin they are much reduced in size, diminishing backwards 
in length in proportion to the reduced height of the fin, and are not 
connected with the sigmoidal extremities of the transverse series of 
plates and rods; neither do their outer extremities appear to articu- 
late with the fin-rays, though there are pretty regularly two rays 
to each plate. The largest of the hour-glass-shaped plates are 2, of 
an inch in length. These, in their arrangement and situation, re- 
semble fin-supports. 
A similar series of hour-glass-shaped plates extends along the 
ventral margin immediately within the base of the anal fin, and are 
large in front for some short distance backwards, corresponding to 
the space occupied by the enlarged anterior portion of the fin. These 
large plates and the large ones at the root of the dorsal seem to be 
articulated with the fin-rays. 
The whole of the transverse plates, areas, and rods, as well as the 
ventral plates and columns and great posterior abdominal rods, seem 
as if covered with black enamel-like matter, having a semigloss si- 
milar in appearance to that which covers the head-bones and fin- 
rays. Indeed some of them seem as if composed of nothing else ; 
and such is the appearance of a few of the cranial bones themselves. 
The bony support, however, can be traced in some of them; and a 
few of the lateral rods are hollow, the bony or cartilaginous support 
having apparently disappeared. But this enamel-like matter does 
not seem to have been confined to these parts ; it appears to have 
been continued as a thin film composed of granules between the 
series of plates, and was extended over the entire surface of the fish 
as a dermal envelope, the plates and rods being, as it were, immersed 
init. Such is the appearance particularly in the region of the sig- 
moidal ridges, where there is a continuous darkish film of consider- 
able thickness, having a granulated surface and giving the appear- 
ance to them of a series of broad continuous plates, which in all 
probability they are, the grooves in the ridges limiting the anterior 
and posterior margins of each plate. And there is usually, extending 
from the margin of the lateral plates, a broken fringe (figs. 2, 3, v) of 
342 
