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128 Bulletin American Mueum of Natural History
[Vol. LIX
part of the posterior part of the skull is missing, and in consequence I
have not been able to develop the palate (which is undoubtedly present
in the positive block). The second specimen (6939+6951) is slightly
smaller in size. Two blocks, upon development, give much of the dorsal
surface of the skull; a portion of the palate has been developed in counterpart
of the more anterior block.
From these two, taken together, the dorsal surface of the skull can be made out
nearly completely. The surface ornamentation consists of deep pits, not very elongate.
The orbits are situated slightly posterior to the middle of the skull, and had a somewhat
subtriangular shape. Septomaxilla were present in the nostrils in both specimens.
The nasals were large and broad; the frontals considerably smaller. The usual
pineal is present, centrally situated between the large parietals. The posterior part
of the table of the skull is absent, and I can say nothing of the structure of the tabulars
and dermal-supraoccipitals. The supratemporal extends forward to about the level
of the pineal; between it and the postfrontal there is interposed an intertemporal,
approximately quadrilateral in shape. The post- and prefrontals are of normal construction;
the lacrymal is a long element with the primitive reach from orbit to nares,
in contrast with such a form as Eogyrinus. There is a broad expanse of bone beneath
the small orbits, across which the very large jugal extends forward to a broad contact
with the lacrymal. The postorbital is roughly triangular in shape, having contacts
with the postorbital and intertemporal above, the supratemporal posteriorly, and
the jugal and squamosal laterally. The quadrate region is obscure as to detail. The
premaxilla is large; its anterior end curves down sharply over the "snout" to the
tooth row. The maxilla is broad anteriorly, but narrows rapidly backwards along its
contact with the jugal.
The marginal teeth are best seen in the smaller specimen. They are
fairly short labyrinthine teeth, somewhat recurved, extraordinarily
stout, and set close together. They are suggestive of an intermediate
stage between the teeth of more typical labyrinthodonts and the small,
closely-set and recurved teeth of Cricotus. These teeth are obviously
identical with the specimen figured by Cope in 1875 as Leptophractus
obsoletus, and are of the same nature as the "Rhizodus" teeth described
by Newberry, which Smith Woodward, in 1891, stated probably were
those of labyrinthodonts.
The anterior portion of the palate is partially shown in the smaller specimen.
Unfortunately the margins are covered by the lower jaws. The surface is slightly
imperfect anteriorly, but it is improbable that a vacuity was present at the anterior
end of the palate.. (There are no enlarged mandibular teeth on the jaw, which
appears to belong to this species.) The prevomers are of very large size, and meet
in a large median suture, while medially and anteriorly they bound the large triangular
internal nares. This margin of the bone is raised into a ridge, at the anterior
end of which is a thenar tooth and pit (both teeth are functioning on the right
side). The palatine appears to form much of the external boundary of the naris;
close to the posterior border of this opening is an elevation with a tooth and pit.