78 S. W. Williston. 
erooved in the middle, shallowly in front, more deeply behind, where 
it is bordered on each side by a descending process which terminates 
in a free thin margin underhanging a fossa that opens backward. I 
cannot distinguish with certainty the sutural division between the 
basisphenoid and basioccipital, though it seems to be wholly back of 
the lateral processes, since in another skull, in which the basioccipital 
has been dislodged, the division has been made back of these processes. 
On either side of the basiphenoid, or the conjoined basiphenoid and 
basioccipital, an elongate, cylindrical or oval rod is given off, which 
is directed downward, outward and backward, lying closely under the 
posterior end of the pterygoid plate, and reaching nearly or quite to 
the head of the quadrate. This process, clearly the stapes, seems to 
be suturally united with the basiphenoid, as indicated in Fig. 1, 
Plate II. The position of the bone in the specimen seems to be 
quite normal and undistorted, and the bone is nearly complete, 
though possibly the extreme end has been broken away; it seems to 
be perforated proximally by a small foramen. The shape, form and 
relations of the basisphenoid, stapes and pterygoids may be compared 
with the author’s figure of the same parts in the remarkable rhachito- 
mous amphibian recently described by myself.’ The basioccipital 
bone, limited as I believe it to be in front, is small and is clearly 
distinguishable from the exoccipitals. Its condyle is convex, oval 
from side to side, somewhat pitted in its middle, and seems to be 
wholly composed of the basioccipital. The exoccipitals are small, 
apparently taking no part in the condyle. The suture limiting them 
from the basioccipital is clearly seen at the sides below and joining 
the margin of the foramen immediately at the side of the condylar 
surface above. The suture separating it from the paroccipital passes 
through the jugular foramen, thence directly upward and forward. 
The exoccipitals join the supraoccipital by a transverse suture a 
little below the summit of the foramen magnum. The foramen 
magnum is heart-shaped, about eight millimeters in its greater diam- 
eter. The paroccipitals or opisthotics are distinct elements, the dis- 
tinguishing suture very clearly indicated, as already stated. They 
are stout at their base, and are turned outward and backward to end 
"Trematops milleri, Journal of Geology, vol. xvii, p. 686, 1909. 
