Wor 3.) - CHEEK AND SHOOT OF AMIA CALVA. 433 
In Amiurus catus, the adnasal bone of McMurrich is said by 
him (No. 24, p. 278) to contain a part of the infraorbital lateral 
canal. It accordingly belongs, if McMurrich is correct, to the 
infraorbital, or antorbital, chain of bones, and not, with the 
nasal, to the supraorbital chain. 
The ethmoid (£7//) of Amia is a median V-shaped bone that 
lies between and in front of the nasals. It rests, as the median 
edges of the nasals do, upon connective tissues that cover the 
dorsal surface of the median, rostral process of the chondro- 
cranium, and, like the nasals, it does not touch the cartilage at 
any place. The anterior end of the rostral process of the 
chondrocranium reaches forward to the point where the two 
arms of the bone diverge, but is not exposed between them on 
the dorsal surface of the skull. The anterior end of each arm 
of the bone rests upon, and is bound by dermal and fibrous 
tissue to, the dorsal surface of the corresponding premaxillary, 
immediately above and behind the teeth of the latter bone. 
Laterally, the anterior end of each arm of the ethmoid touches, 
and is bound by dermal tissue to, the anterior end of the corre- 
sponding antorbital bone. The bone is traversed by the ante- 
rior cross-commissure of the infraorbital lateral canal, and, 
being developed in connection with that canal, is unquestionably 
formed by the fusion of two lateral components, one on each 
side of the head. 
In Polypterus, according to Pollard (No. 30, p. 400), there is, 
as in Amia, a median, dermal ethmoid, traversed, as in Amia, 
by the anterior cross-commissure of the infraorbital canal. 
According to Traquair (No. 44, p. 171), this bone is of primary 
origin, but has a flat, narrow, posterior process which ossifies 
“in the membrane superficial to the cartilage.” According to 
Pollard, the bone lies wholly on the dorsal surface of the skull. 
According to Traquair, it forms part of the ventral as well as 
part of the dorsal surface of the skull. According to Erdl (No. 
13, p. 242), it is the homologue of the vomer bone of other fishes, 
and is not in any sense an ethmoid bone. 
In teleosts, the so-called ethmoid is said to be sometimes a 
purely dermal bone (No. 26); sometimes partly of dermal and 
partly of cartilaginous origin; sometimes entirely of cartilaginous 
