Cope.] 574. [March 7, 
The orbit occupies part of the anterior third of the length. It is bounded 
in front by an obtuse preorbital process, and posteriorly by a laterally 
expanded and decurved postorbital process. The latter*bears an articular 
facet on its posterior and inferior face. The top of the muzzle is exca- 
vated by a fontanelle which does not extend posterior to a line connecting 
the preorbital processes, 
Thereis a prominent cup-shaped occipital condyle. On each side of 
the cranium a short distance anterior to it, is a prominent process extend- 
ing outwards and a little backwards, which is excavated on its inferior 
side, but whose posterior side is decurved, so that the inferior concavity 
looks partially forwards. Into this cavity, and abutting against the 
decurved posterior edge, is a lateral process of the basal axial bone of the 
skull, which I take to be homologous with the lateral alee which occupy 
the same position in the sharks. Anterior to this junction no doubt the 
hyomandibular bone was suspended, for I suspect that it was articulated to 
a small condyle which is wedged into the fissure between the inferior and 
superior elements described, a centimeter anterior to their posterior 
extremities. This condyle is a distinct clement of a subglobular form. 
The interorbital plane is continued posteriorly, bounded on each side by 
a depression which probably corresponds to the temporal fossa of higher 
vertebrates, The edges of this plane are thus well within the lateral 
borders of the cranium. The plane rises a little posteriorly, and is split 
into two narrow wedge-shaped processes, which project freely upwards 
and backwards, The rather short remaining part of the roof of the skull 
has a keel or sagittal crest on the middle line, which descends gradually 
to the foramen magnum. 
The base of the skull forms a continuum from the edge of the large occi- 
pital cotylus to the acuminate anterior extremity. The lateral basal ale 
are subcylindric, and are separated from the basicranial axis by a fissure 
for a short distance, and then unite with it. Two or three foramina ante- 
rior to this reunion, are in line with the defining fissure just mentioned. 
The basis cranii sends out a process on each side below the postorbital 
processes, giving a cross-shape to this part of the base of the skull. An- 
terior to this point it is free from other elements and contracts to an 
acuminate apex, 
The cranium is segmented, but a clean specimen is necessary to per- 
mit the straight sutures to be seen. In the first. place, there is a distinct 
occipital bone, which includes exoccipital and basioccipital elements com- 
bined. The latter includes the large occipital cotylus, as in the Rhachi- 
tomous batrachian Trimerorhachis, and difters from the structure seen in 
the Lepidosirenide, where exoccipital elements only are present. ‘The 
occipital extends but a short distance on the inferior face of the axis. It 
is preceded directly, and without imbrication, by a continuous axial ele- 
ment, If we recognize in the granular character of the tissue evidence 
of true ossification of the chondrocranium, we have here true continuous 
sphenoid and presphenoid bones, 
