1909.] OLFACTORY ORGAN OF TELBOSTEAN FISHES. 621 



conical lip and is separated by a deep gutter from the front edge 

 of the posterior nostril, which is raised to form a valve-like 

 flap that probably covers the posterior nostril in inspiration 

 (text-fig. 193). 



Olupeidje. 

 Clupea harengios. 



The nostrils are very similar in form, m.utnal relations, and 

 position to those of the Salmonidpe examined, particularly to 

 those of Goregonus. The olfactory cavity is also closely similar, 

 being produced towards the orbit to form an extensive though 

 laterally flattened sac, which is prolonged both above and below 

 the eye. The lower border of the sac is compressed by the upper 

 edge of the mandible when the mouth is closed. 



Clupea spratius does not differ from the Herring, 



Chirocentrtd^. 

 Chirocentrus dorab *. 



The olfactory organ is essentially the same as in Clupea 

 allowing for alterations in the form of the cavity due to the 

 relative shortening of the space between the ethmo-palatine 

 articulation and the orbit. The olfactory laminse are also less 

 strongly defined than in Clupea and sink more gradually at the 

 periphery of the rosette area into the general lining of the nasal 

 cavity. 



MORMYRID^. 



Mormyrus sp. 



The nostrils lie about halfway between the eye and the snout 

 set obliquely, the posterior some few millimetres behind and 

 slightly below the anterior. Both are simple perforations, the 

 anterior minute and circular, the posterior larger and oval, with 

 a slightly swollen boi'der. 



The olfactory chamber is circular and laterally compressed ; 

 its floor (mesial surface) is completely covei'ed by a circulai- 

 rosette. There are no accessory sacs. 



The rosette consists of from 12-16 laminae radiating from a 

 well-marked median raphe connected in front with the anterior 

 lip of the anterior nostril. The individual laminse are low with 

 a swollen and gently convex free border, 



Gymnarchus niloticus. 



The olfactory organ is much the same as in Mormyrus though 

 its cavity is more elongated and has a considerable empty space 

 between the rosette and the posterior nostril (text-fig. 194). The 

 anterior nostril also is surrounded by a short tubular lip elevated 



* For this specimen I am iii(Jebtecl to Col, C. E, Sliepherd, 



