No. 3.] CHEEK AND SNOUT OF AMIA CALVA. 45I 
through the premaxillary entered at once the vomer without 
piercing at all the cartilage that forms the floor of the olfactory 
pit, as it did in the first specimens examined. The canal in this 
specimen thus lay entirely anterior to the cartilage of the chon- 
drocranium, and the anterior end of the palatine nerve ran 
upward in front of the anterior edge of the chondrocranium, as 
it did also in all the larvae examined. The nerve, also, in this 
specimen, did not reach the level of the upper surface of the 
premaxillary, but appeared on the dorsal surface of that bone at 
the hind end of a short groove or pit, at the anterior end of 
which another foramen, corresponding to the separate anterior 
foramina of the first specimens examined, led into the pre- 
maxillary. The enclosing of the distal end of the anterior 
branch of the palatine nerve in a cartilaginous canal thus seems 
to be a secondary process belonging to post-larval stages. 
The mesial end of the anterior, alveolar portion of the pre- 
maxillary lies directly beneath and gives support to the antero- 
lateral end of the ethmoid, the two bones being, in one large 
specimen, firmly connected by partial anchylosis. The anterior 
end of the antorbital rests upon the dorsal surface of the pre- 
maxillary immediately lateral to the lateral end of the ethmoid. 
The nasal lies dorsal to the spoon-shaped portion of the bone, 
but separated from it by the nasal sac. The posterior portion 
of the mesial half of the ventral surface of the anterior part of 
the bone is roughened, and rests directly upon a corresponding 
portion of the dorsal surface of the anterior end of the vomer, 
the two surfaces adhering closely to each other and seeming to 
be in process of anchylosis. Lateral to this roughened surface 
there is, on the ventral surface of the bone, a sharply depressed, 
almost pit-like region, which extends to the lateral edge of the 
bone. It forms the anterior and dorsal surfaces of an articular 
pocket which receives the anterior articular end of the maxillary. 
The anterior edge of the septomaxillary forms the posterior sur- 
face of this pocket, and a slight transverse groove on the dorsal 
surface of the vomer its ventral surface. 
In Polypterus the premaxillary lies, according to Traquair 
(No. 44, Figs. 1 and 5), external to the ethmoid bone, not only 
on the dorsal surface of the skull, but also on its ventral surface. 
