18 FIELD CoLUMBIAN MuszEUM—GEOLOGY, VOL. II. 
The supraorbital forms, as already stated, a horizontal plate 
extending out over the orbit in front. Its union with the prefrontal 
posteriorly is obscured by fracture, but indications of a suture are 
seen anteriorly. Between this bone and the postorbital there is a 
deep notch, angulated externally. The suture between the prefrontal 
and supraorbital is clearly seen anteriorly, running from the small 
foramen already mentioned forward and outward to terminate near 
the maxilla, at the posterior end of the nares. The connection of the 
bone with the maxilla can not be made out, as there has been an 
infolding here; its connecting suture with the ascending process of 
the maxilla is, however, well defined, running obliquely forward. | 
The descending plate of the supraorbital has, in its orbital margin 
near the upper part, a small foramen, piercing the bone obliquely. 
The horizontal portion terminates anteriorly by sinking to the surface 
of the descending portion. The whole bone reminds one of the pre- 
frontal of C@dasfes. 
The fostorbital bone is a narrow, elongate and thin bone, united 
above with the postfrontal, and to a slight extent with the parietal, 
near the top of the epipterygoid; below to the jugal. On the right 
side, this bone, like the postprefrontal and jugal, has been macerated 
away, and, although somewhat distorted, presents no evidence of 
being composed of more than one element. 
In the above description of these frontal elements, I have fol- 
lowed the usual determinations, but |am not satisfied withthem. The 
‘“supraorbital,”” though occupying the position usual for this bone 
above the orbit, has relations anteriorly that are altogether unusual ; 
the nasal and the lachrymal do not appear to exist as independent 
elements. It would seem more likely that this supposed ‘‘supra- - 
orbital” is really the lachrymal, if the postfrontal and prefrontal are 
fused into one element. Again, such a combination of the postfrontal 
and prefrontal and their pecular articulations is remarkable. The 
very narrow frontal, while showing a distinct suture in the middle, 
presents no evidence of any connection with the parietal —it seems 
more to be a very narrow rostrum projecting in front of the parietal 
and separating the bones, which otherwise would answer very well 
for frontals. In this latter case, the so-called ‘‘supraorbital” would 
really be the prefrontal, and the postorbital the postfrontal. or post- 
fronto-orbital. This may seem a violent supposition, but it does not 
seem at all improbable to me. Nor is the union of the parietal with ~ 
the premaxilla any more extraordinary than is the union of the supra- 
occipital with the frontal in many Cetacea. 
Sclerotic plates are present in the left orbit of this specimen in a 
