<= 
54 FirLp CoLtumBian MustuM—GEocoey, VoL. II. 
suture beginning just back of the sixth tooth. The distinguishing 
suture turns upward and backward to meet the anterior end of the 
external nares in front of the orbit. Above this, for a short distance, 
the bone is so crushed that the suture is not determinable with cer- 
tainty, but the upper end is evident, nearly above the middle of the 
orbit. The suture ‘separating the two premaxille is distinct 
throughout. 
The maxilla has on each side sockets for twelve or thirteen teeth, 
all, except a few of the anterior ones, much smaller than those of the 
premaxilla, and smaller than those of the mandible in this region. 
From the nares, which are chiefly excavated from this bone, the 
suture turns upward and backward for about twelve millimeters, sep- 
arating the nasals; it then turns downward and backward to join the 
anterior orbital margin, uniting with the prefrontal. The lower 
anterior margin of the orbit is thus formed by.the maxillary plate, 
which shows a shallow groove. The maxillary plate on the left is 
smooth and undistorted, the nasal and prefrontal having been sepa- 
rated at their sutures. There is no indication whatever of a separa- 
tion into two elements, nor is’ there any free lachrymal. Posteriorly 
the maxilla forms a rather broad plate below the orbits, having a 
convex thinned margin continuous with that of the jugal. Back of 
the middle on this margin, the suture for the jugal turns directly 
downward for about twelve millimeters, and then backward in a 
straight line to terminate just beyond the last tooth. 
That element which, in Dolichorhynchops, is described as the 
supraorbital, is a much more massive bone in C7molasaurus. It 
unites with the postorbital by a strong suture, behind the middle of 
the orbit above, and is not separated by a deep notch as in that 
species. The bone arches forward and downward to beyond the 
middle of the anterior part of the orbit, as in Dolichorhynchops, stand- 
ing out prominently over the orbit and terminates in a strong suture 
by which it is united to the ascending plate of the maxilla, as has 
been described. Its union with the prefrontal or frontal cannot be 
determined in the crushed state of the specimen. Such relations of 
a supraorbital bone with the postorbital, maxilla, nasal, etc., are almost 
inconceivable, but are altogether right for a prefrontal. If this bea 
prefrontal, then the same element in Dolichorhynchops must also be 
the prefrontal, and the so-called postprefrontonasal is in reality the 
frontal, while the anterior prolongation from the parietal is in reality 
a process from that bone, separating the frontals, a most remarkable 
arrangement for any vertebrate skull. I am forced to believe, how- 
ever, that such is really the explanation of these bones. 
ee 
