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PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 265 
tion; below it appears to have more of a pentagonal outline on account 
of the less irregularity of the surface near the contour. 
The notochord is persistent in the skull for half the length of the basi- 
occipital. 
The occipital condyle is transverse and there are no lateral ones. 
The basioccipital occupies nearly a third of the length of the base of 
the cranium. ; 
There is a very small supraoccipital developed as a transverse bone 
above the foramen magnum and protruded forward as a triangular 
wedge between the parietals. 
External to the exoccipital there is an opisthotic element, in front of 
which succeeds a discoidal element (which is probably the proétic) with 
which alone the hyomandibular articulates, not coming in contact with 
any other otic bones. 
There are well-marked exoccipitals and alisphenoids which have more 
or less distinct sutural relations with adjoining bones, but their limits 
have not been clearly determined. 
External to the parietals there is a pterotic with lateral and ventral 
fossxe for the insertion of the strong muscles which move the jaws. 
The parasphenoid is present and extends as a narrow splint from the 
hinder portion of the basioccipital to very near the end of the rostrum, 
where it widens and assumes a slightly spatulate form, resting free on 
the ethmoid expansion, there being no vomer developed. 
The presphenoid has not been worked as to its limits anteriorly, but 
the fifth nerve passes out of the skull behind the alisphenoid in its usual 
relative position to other parts and immediately within and in front of 
the discoidal element lodged in a fossa behind the alisphenoi@ and be- 
low the pterotic, and with which the styliform hyomandibular has an 
articulation admitting of a swinging movement, inasmuch as the pter- 
otic itself is slightly mobile in relation to the adjacent bones. 
The parietals are the best developed bones, aud cover most of the 
hinder half of the cranium, those ot the two sides being in contact from 
near the foramen to near the center of the roof. 
In front of the parietals there are postfrontals which form laterally 
the posterior border of the orbit. 
The ethmoid o¢ rostral part of the cranium is cartilaginous or like the 
chondrocranium of the typical teleost in its histological characters. 
The orbital fosse open obliquely forwards and directly downwards, 
and there are no infraorbital bones. 
The nasal fosse are depressed excavations in the lateral region of the 
cranial rostrum, partly roofed over above and from behind by horizon- 
taliy projecting cartilaginous ridges; they open obliquely forwards and 
outwards within a very short distance of the upper side of the end of 
the snout. 
The foramen for the passage of the ninth and tenth nerves opens 
alongside the basioccipital and perforates the exoccipital. 
