NO. 3] LATERAL LINE OF AMIA. 479 
bone, somewhat triangular in shape, exactly filling a large notch 
extending from the middle of the lateral edge of the frontal to 
the hind edge of the bone. Its small posterior end usually fits 
into a notch in the anterior end of the squamosal, which over- 
laps somewhat its lateral edge. It rests directly upon the deeper 
postorbital ossification, and is so closely connected with it, that 
in attempting to remove it in fresh specimens, one of the bones 
is usually broken, and a fractured surface obtained; but in skel- 
etons properly prepared,— by maceration or by boiling, — the 
ag 2a out 
we wwe 
Pi Ae al 
Lat 
Ee 
Cut 2.— A, top view of frontal, postfrontal, prefrontal, and squamosal bones, 
showing the postorbital ossification in place; 4, side view of same; C, top view of 
postorbital ossification after removing the dermal bones; ZY, top view of prefrontal 
after removing the frontal; /*, frontal; zf c, infra-orbital canal; om. c, operculo- 
mandibular canal; vf, prefrontal; psf, postfrontal; /s¢, postorbital ossification; 
spc, spiracular canal; sg, squamosal. 
two bones are easily parted, leaving a clean and perfect surface 
of separation. The postfrontal projects beyond the postorbital 
ossification in front, and forms part of the roof of the orbit. 
The lateral edge of this part of the bone is thickened, frequently 
having a rib-like projection along its under surface, as if the 
edge of the bone had been turned down and a little under. 
The upper corner of this thickened edge and the corners of 
