173 
palatine bone. In front a portion is sent upwards inter- 
nally at right-angles to the main portion and internally to 
the palatine. This soon terminates, and the remainder of 
the sac ends bluntly below the palatine. 
Postero-ventral nasal sac (7. sac.*)—Opens into the 
nasal chamber as above described. It is ver} irregular in 
shape, and three-rayed in transverse section. It passes 
far backwards just above the mucous membrane and to the 
right of the palatine, being narrow behind and ending 
blindly just over the mucous membrane of the mouth 
below and internal to the sclerotic of the right eye. 
Gent, Oliactory Organ . 
The anterior and posterior nostrils (a. nos.', p. nos.*) 
are no different from those of the right side, except that 
the anterior tube is smaller and the posterior nostril is 
larger and more widely open. 
The left nose is situated at a transverse level posterior 
to that of the right, and is further much less developed. 
This is most evident in the nasal chamber (n. ch.!), which 
is obviously smaller and was in the sections only thrown 
into 4 olfactory lamine (0. /am.'), the dorsal one of these 
being quite small and the ventral one smaller than the 
two intermediate lamine.* The figure does not admit of a 
comparison as regards the nasal sacs, since their dimen- 
sions from above downwards cannot be shown. 
There are only two nasal sacs on the left side as 
follows :— 
Dorsal nasal sac (n. sac.‘).—Arises from the nasal 
chamber dorsally from behind. At first its shape in trans- 
verse section is that of an inverted right-angle—the verti- 
*The difference between the two olfactory organs is seen in the 
diameter of the right and left olfactory nerves (fig. 25, 7. olf., n. olf.'). 
The figure only illustrates the difference in diameter, the difference in 
bulk is even greater. 
