1909.] 



OLFACaX)RY ORGAN OF TELEOSTEAN FISHES. 



635 



Exocoetus volitans. 



The olfactory organ is similar to that of Hemirhamphus. It is 

 worthy of notice that in Hemirhaimphus and Exoccetios the tubules 

 of the lateral line that traverse the lachrymal bone open directly 

 into the lower part of the olfactory chamber. This probably 

 indicates that the single opening of the olfactory pit is not primi- 

 tive, but a secondary modification, the original openings having 

 spread to include within the pit what at one time was the external 

 surface of the face. 



MUGILID^. 



Mugil chelo. 



The nostrils lie about halfway between the eye and the 

 snout, bounded as usual by the lachrymal and nasal bones. The 

 anterior nostril is circular, with a short tubular lip higher behind 

 than in front. It is separated by a bridge of skin about twice its 



Text-fig. 204. 



\R.PMX. 



Mugil chelo. 



A. The olfactoi'3' organ, in position, from the side. 



B. The same, from above. 



diameter in breadth from the posterior nostril, which is a vertical 

 slit protected from ingress by a thin, transparent valvular exten- 

 sion of its anterior border. 



The olfactory chamber is oval and of the same length as the 

 space between the nostrils. It lies in the usual hollow in '^the 

 ethmoid behind the maxillary process of the palatine. Its hinder 

 parts, which are unoccupied by the rosette, extend for some little 



