436 
This tube runs outward and forward and opens on the outer surface 
of the head by a single pore which lies immediately mesial to the 
anterior edge of the nasal tube. This tube and its associated pore, 
although actually the first ones in the line, are, in reality, numerically 
the second ones, for a tube and pore have disappeared in the median 
line where the canals of opposite sides unite. This is definitely shown 
by the two sense organs, 
zZ one on each side of the 
BR apts ZART : : 
EN AN OF middle line, found in 
[es OS Oa a) 7,7 Sun the canal that traverses 
ae ee the ethmoid, one of these 
organs belonging to one 
side of the head and the 
other to the other side, 
and there being no tube 
and pore between them. 
Such a tube and pore 
have here necessarily 
disappeared, as they do 
in the same place in 
Amia (No. 2). 
The tube that issues 
from the canal of either 
side between this eth- 
Fig. 2. „= Hig 3. 
Fig. 2. Top view of the same, 
Fig. 3. View of the internal surface of the second supratemporal ossiele of a 30-cm 
specimen of Polypterus bichir. 
ahl anterior horizontal cheek line of pit organs, al anterior head line of pit organs. 
ana anterior nasal aperture. ANA accessory nasal bone. ART articular, D dentary. 
ETH ethmoid. FR frontal. io sense organs of infraorbital canal. ip pores of infraorbital 
canal, LA lachrymal. m! middle head line of pit organs. MX maxillary. NA nasal. 
OT os terminale. phl posterior horizontal cheek line of pit organs, pmo sense organs 
of preoperculo-mandibular canal, pmp pores of preoperculo-mandibular canal. PMX pre- 
maxillary, POP preoperculum. POR postorbital bone. PSF postfrontal. PSZ post- 
temporal. so sense organs of supraorbital canal. sp pores of supraorbital canal. SQ.PA 
squamoso-parietal, SZ'1—° supratemporal ossicles, sto sense organs of supratemporal 
commissure. stp pores of supratemporal commissure. vw vertical cheek line of pit organs, 
Figs. 1 and 2 are natural size. Fig. 3 is >< 5. 
