8 ON THE STRUCTURE OF EUSTHENOPTERON 
aspect there is a large subtriangular median bone, the dermo- 
supraoccipital, on each side of which are the quadrangular tab- 
ulars. In advance of these are the long and rather narrow par- 
ietals, bounded on either side by two smaller bones, the intertem- 
poral and the supratemporal. These six latter bones were firmly 
united by sutures into a continuous shield nearly flat on top and 
curved on the sides. In adult individuals the sutures are obliter- 
ated externally and the individual bones are only obscurely indi- 
cated by the arrangement of the ornament. 
In advance of the parietals and loosely articulated to them and 
to the intertemporals are the frontals. These are closely united 
by a suture in the median line except at one point about opposite 
the posterior margins of the orbits where there is a pineal open- 
ing. As it is not elevated above the surrounding surface extern- 
ally and there is no modification in the arrangement of the orn- 
amental tubercules the opening is more readily observed from 
below, where it is wider. It is well shown in the specimen pho- 
tographed on Plate 3, fig. 2. The frontals are notched anteriorly 
to receive the large median bone which | call the interfrontal, and 
which may be the homolog of a median ossification occuring in 
the Palaeoniscidae, sturgeons and many teleosts 1. e., the tarpon, 
and called by Traquair the super-ethmoid. 
This membrane bone is sometimes named mesethmoid by authors 
in teleosts, but the true mesethmoid is a cartilaginous element 
lying beneath it. “It has very much the position of the dermal 
bone named by Broom interfrontal in Eryops, except that in 
Stegocephalians, in correlation with the great extension of the 
olfactory region, the nasals have gained contact in front of the 
interfrontal, which is now a small element and subsequently 
disappears.” (Gregory, 1918.) 
There is a singular lack of rigidity in the connection between 
the parietals and frontals which is remarkable in view of their 
relation to the brain case. In Osteolepis also, what seems to be a 
pineal foramen occurs at a point between the frontals far in 
advance of their junction with the parietals. This apparently 
flexible union between the frontal and parietal regions occurs in 
other members of the family i. e., Holoptychius and Glyptopomus. 
In the fossils there is nearly always a dislocation at this point 
which causes the front of the skull to appear more depressed than 
was actually the case in life. I shall have occasion to refer again 
