178 
ACTi:S’OPTERTGII. 
those ill advance of the pelvic fins being conoparatively 
slender. Most of those in the caudal region are exposed 
from the inner aspect, and the uncinate spine is thus 
only visible on a few dorsal scutes of the caudal pedicle. 
There are traces of scutes on the flanks, but they are not 
distinct. Lewis Coll. 
49541. Equally large fish, the head and anterior abdominal region 
exposed from below, the remainder of the trunk from the 
side ; Sahel A^ma. The imperfect long and slender man¬ 
dible is shown from below, the ramus of the right side with 
five large pits in sparse longitudinal series at its anterior 
end. A fracture seems to indicate the division between 
the dentary and articulo-augular elements ; if so, the 
latter is almost as long as the former. Traces of very 
slender branchiostegal rays are observed behind, seven 
being indicated on the right, and possibly more on the 
left side. Slightly more than seventy vertebrse can be 
counted, and some of the characteristic centra in the 
anterior abdominal region exhibit the laminar transverse 
processes. The pectoral fins are imperfectly preserved on 
each side of the trunk, and that of the right distinctly 
indicates eleven rays, the hindermost excessively delicate. 
The pelvic fins are shown only in a fragment opposite 
the anterior end of the dorsal fin, of which the foremost 
nine or ten rays are preserved. The anal fin is almost 
destroyed, but the caudal fin is not much injured. The 
marginal scutes are of the usual form and proportions, 
distinctly in continuous series along the base of the dorsal 
and anal fins; some on the ventral border of the mid- 
caudal region are exposed in side-view and display the 
relatively large uncinate spine, which becomes greatly 
reduced on the corresponding scutes of the caudal pedicle. 
The appearances on the flank are difiicult of interpreta¬ 
tion; but below the vertebral column just behind the 
pectoral fins there is a series of narrow heart-shaped 
scutes shown from the inner face, which seem to have 
borne a median longitudinal keel; and below these again, 
especially a little further hack, there are traces of the 
oblique lath-shaped plates, which are still better observed 
on the caudal region. At the base of the anal fin, 
indeed, three of these lath-shaped plates seem to be 
directly continuous with the postero-superiorly inclined 
