1909.] OLFACTORY ORGAN OF TELEOSTEAN FISHES. 655 



mandibulfe. It reaches in front into the angle between the 

 maxillary process of the palatine and the maxilla, and is bounded 

 internally by the buccal membrane. A small ethmoidal sac is 

 also present, formed by an extension of the upj)er part of the 

 olfactory chamber forwards around the backward process of the 

 premaxilla. 



The sacs are compressed by the premaxilla and maxilla as 

 these bones move in the closure of the mouth. 



Sximmary. 



In comparing these two representatives of the Jugulares the 

 difference in the structure of the i-osette should be particularly 

 noticed. In Bovichthys this has the peculiar characters of that 

 of Cottus (Blaue), while in Trachinus it is of the normal oval 

 type. 



Pediculati. 



LOPHIID^. 



Lophms piscatorius. 



The olfactory organ of Lophvus has been described in detail by 

 Miss Pereyaslawzeff, so that it is sufficient to mention that it is 

 in a degenerate condition, consisting of only a small olfactory 

 chamber set on the end of a short tentacle standing up from the 

 dorsal surface of the face close behind the ethmo-palatine 

 articulation. 



The cavity of the chamber is filled by a few (four or five) sharply 

 convex laminse set longitudinally parallel to one another. The 

 olfactory nerve takes a most unusual course between the base of 

 the olfactory tentacle and brain. It at first dips down between 

 the ethmo-maxillary ligament and the raised outer border of the 

 ethmoid, then passing outwards through this bone to the lateral 

 surface of the cranium, runs backwards within the orbit between 

 the roots of the oblique muscles, and finally enters the brain-case 

 just in front of the origin of the recti. 



Morphological Sicmmary. 



The most important facts detailed in the above descriptions 

 can be most clearly summarized in a table (pp. 656-7). 



A consideration of the foregoing shows that the nose can be 

 divided into two parts, one of which is practically constant and 

 forms the essential part of the organ, while the other is of 

 secondary importance, and may be present or not. These are the 

 olfactory chamber with its rosette and the accessory nasal sacs. 



The olfactory chamber differs comparatively little in shape and 

 relative size, and in nearly every case occupies a constant and 

 fixed position with regard to the bones of the skull, being lodged 

 in a hollow in the ethmoid between its points of articulation with 

 the palatine and the lachrymal bones. In nearly all cases it 



