1871.] 345 [Cope. 
The premavillary is several times longer than wide; posteriorly it 
is a subvertical plate ; anteriorly it terminates in a narrow obtuse por- 
tion. Just behind this portion it is enlarged on the inner side, forming a 
knob, whose upper surface supports the articulation with the ethmoid. 
It bears the two large teeth below, on a common elevation of the jaw. 
The outer margin of the bone supports ten sub-equal teeth, which are one- 
third smaller than the posterior pair. The outer alveolar ridge is a little 
more elevated than the inner, though a little less so than on other bones 
which support teeth. The external face of the bone is nearly smooth, 
and the inner unites with the maxillary by striate squamosal suture. 
The maxillary preserved is nearly perfect, and may belong to another 
animal; its depth coincides with that of the premaxillary. It is quite 
elongate, about nine times as long as deep, perhaps a little more. It sup- 
ports forty-two closely packed teeth, not all in functional service at once. 
The distal end is contracted and grooved and ridged on the inner face, as 
though for union with a supernumerary bone. The external face is lon- 
gitudinally striate on the posterior half, the striz running out to the mar- 
gins, forming sharp rugosities on the alveolar border. The superior 
(palatine) articular surface is more than one-fourth the total length from 
the anterior extremity ; it is narrow and somewhat lens-shaped. Both 
behind and in front of it, strong striae run from the outer to the inner 
side of the superior margin, sub-longitudinally. Posterior to the superior 
articular surface on the outer face is a swelling like a muscular impres- 
sion, from which grooves and keel extend posteriorly. The bone is con- 
“cave on the outer face in front, to accommodate the os premaxillare. 
The mandibular rami are abruptly incurved at the symphysis, which is 
not serrate, is sub-round, with an emargination entering from the inner 
inferior side. The dentary bone is much narrowed behind. The angular 
bone extends anteriorly on the inner face to the end of the posterior, two- 
fifths of the dental line. The ramus is not very deep at the coronoid 
region. The articular cotylus is composed more largely of the angular 
than the articular. Its long diameter extends inwards and backwards, 
and is strongly convex ; in the transverse direction, slightly concave. 
Below and in front of it the lower margin of the jaw is acute. The angle 
is oval and rather small, it is prominent on the middle line on the inner 
‘Side, the edges are thin, the upper curved outwards, concealing part of 
the cotylus. There are twenty-nine teeth on the dentary, whose sizes 
diminish towards its extremities. Their roots are very large and longitu- 
dinally striate and porous. Opposite the interval between the first two 
teeth, there is a tooth exterior to the general row, and another on its in- 
ner side. They are not enlarged. 
No teeth are preserved except on the maxillary. These are not very 
» elongate cones, with round section, and well curved inwards. Dense ex- 
ternal layer entirely smooth. 
n + : e “of : . . 
This species differs from the type P. basalis, Dixon, in that the radical 
Portion of the tooth is less swollen, and more conic, and does not project 
above the exterior alveolar wall as in that fish. 
A. P. §.—VOL. XII.—2R 
