76 S. W. Williston. 
membrane bones of the cranial wall. These bones unite at their outer 
end with the upper part of the so-called epiotic; the lower, thin and 
somewhat concave border, is free. The epiotics are broader and 
longer than this “postparietal,” with nearly parallel sides, the lower 
margin thinned and free and concave in outline, the upper uniting 
by suture with the squamosal at the angle of the skull. The inner 
end, which is truncate, unites above with the “‘postparietal ;” below 
it presents an oblique articular facet for union with the extremity of 
the paroccipital. The outer extremity is rounded below, and extends 
to the angle of the skull, articulating apparently with the posterior 
end. of the jugal. On its inner surface near the roof it articulates 
for a large part of its extent with the hind border of the quadrate. 
Further observations on the homologies of this remarkable bone 
will be given later. 
The more complete of the two larger skulls has the palatal and 
basicranial regions in excellent preservation, and but little distorted. 
Just back of the transverse bones a recent fracture through the nar- 
rowest parts of the free pterygoids has permitted the removal of the 
posterior portion and its complete separation from the encrusting 
matrix, both above and below, enabling one for almost the first time 
to obtain a clear conception of the cranial bones and their relations to 
each other. Very remarkable is the fact that all this portion has no 
sutural connection with the cranial walls, the suture between the 
quadrate and the epiotic being the only one, indirectly connecting 
the vertebral elements with the superior membrane bones. This will 
readily account for the fact, so often observed, of the loss of the 
basioccipital and basisphenoid from the remainder of the skull, a 
loss which, erroneously interpreted, induced Cope to give the name 
Cotylosauria to the whole group. Above, in the middle, the “post- 
parietals” merely touch the supraoecipital while the epipterygoids 
further in advance touch the parietals in a mere rounded point. 
The quadrate bone of the left side in this specimen lacks its 
articular head, which had been, unfortunately, broken off with a part 
of the articular and lost before the discovery of the specimen. The 
remainder of the quadrate, however, is quite in position, overlapping 
the pterygoids, and is complete. On the right side the quadrate, 
