432 ALLIS. [Vo. XIV. 
preorbital ossifications are generally considered as, and probably 
are, the homologues of the lateral masses of the ethmoid bone 
of man, the two processes of the two frontals of Amia corre- 
spond, one or both of them, to the nasal spine or nasal process 
of the single frontal bone of the adult man. 
Between the nasal of Amia and the body of the frontal there 
is everywhere a relatively wide strip of tough dermal tissue. 
Medianly, the nasal adjoins its fellow of the opposite side of 
the head, the two bones resting upon connective tissue that 
covers the narrow, dorsal edge of the median, cartilaginous wall 
that separates the nasal fossae. To all the bones that adjoin 
it, excepting only the frontal, the nasal is bound by tough 
fibrous tissue, and it nowhere rests directly upon the cartilage 
of the chondrocranium. It is traversed by the anterior part of 
the supraorbital lateral canal. 
In Polypterus (No. 44, p. 173), instead of a single nasal bone 
on each side of the head, as in Amia, there are two such bones, 
both of which are said to be traversed by the supraorbital lateral 
canal. In front of the anterior, or accessory-nasal bone the 
supraorbital canals of opposite sides of the head are said to form 
a transverse commissure through the ethmoid. Connected with 
the anterior nasal there is a small bone said by Traquair to be 
“connected with the termination of the main lateral mucous 
canal of each side.” It is called by him the os terminale. By 
Erdl (No. 13, p. 242) it is considered as the true nasal bone, the 
large posterior nasal bone of Traquair being considered as the 
pars nasalis ossis frontis. From the somewhat indefinite descrip- 
tions of it, it seems to have no separate homologue in Amia. 
In Lepidosteus, as in Polypterus, there are two nasal bones 
on each side of the head, the larger and posterior of the two 
being called by Parker the ethmo-nasal (No. 28, p. 477). The 
latter bone is said by van Wijhe to be traversed by the supra- 
orbital lateral canal (No. 48, p. 273). Whether the smaller, 
anterior bone is or is not so traversed is not stated by van 
Wijhe, and is uncertain both in his descriptions and in Parker’s 
figures. A sketch that I have, made several years ago, of a 
young Lepidosteus shows a canal in the bone in question, but 
leaves it wholly uncertain to which of the main canals it belongs. 
