Most of the ventral surface is covered with minute granular
teeth. The anterior margin is flared and curved posteromedially from the
lateral margin to a median triangular projection. The lateral margins
curve smoothly from the greatest anterior width to the narrow central
portion, where the margins become somewhat thickened and turned
dorsally. Posterior to this the lateral margins are probably nearly
straight. The external surface of the anterior section is nearly flat
and has a central depressed area the sides of which slope evenly to the
center. The internal surface is smooth and centrally convex. Because of
the fragmentary nature of all four observed specimens, total length was
not measured but is estimated to be 15 to 20 mm. The opening of the
hypophyseal canal was not present, possibly because of crushing.
Ethmoidal ossifications were not preserved in any of the specimens
studied. The parasphenoid differs from that of _Rhabdoderma elegans_
(Newberry) in being more flared and widened anteriorly and more concave
centrally.

_Dermal bones of the skull_

Various portions of the cranial roof are preserved in several specimens
(see fig. 3). For comparisons with _Rhabdoderma elegans_, see Moy-Thomas
(1937:fig. 1).

The premaxillaries and rostral elements are not preserved in any of the
specimens. Only one pair of relatively large frontals have been
observed; they are 5.5 to 9.0 mm. long and 2.0 to 3.5 mm. wide. These
are nearly flat bones, with the greatest width posteriorly 0.1 to 1.0
mm. wider than the anterior portion. The midline suture is straight, the
lateral margins are nearly straight, the anterior margin slopes evenly
posterolaterally, and the posterior margin is slightly convex to
straight. The anterior margin in _R. elegans_ is essentially straight.
Ornamentation consists of sparse, unevenly spaced, coarse tubercles or
short striae. In one specimen both bones have small clusters of
tubercles near the lateral margins and about 2.0 mm. from the posterior
margin. None of these bones has alisphenoids or ridges on the ventral
surface, as Stensioe (1921:65, 97) described for _Wimania_ and _Axelia_.

[Illustration: FIG. 3. _Synaptotylus newelli_ (Hibbard). Diagram of the
dermal bones of the skull, in lateral view, based on K. U. nos. 788 and
11432. x 2-1/2 approximately.]

Only six supraorbitals have been preserved (see fig. 3). These are
nearly square, flat, thin bones lying nearly in place adjacent to a
fr