1909.] OLFACTORY ORGAN OF TELEOSTEAN FISHES. 629 



directed forward. The anterior border of the narrow bridge of 

 skin between the two is sharply deflected into the nasal cavity. 



The olfactory chamber occupies the normal position with regard 

 to the bones of the skull, and is a shallow oval cavity coiresponding 

 to the area covered by the nostrils. Its floor is covered by a 

 peculiarly insignificant circular rosette in which the laminfe are 

 low folds of the mucus membrane differing amongst themselves 

 in importance and radiating from a central boss situated directly 

 below the anterior nostril and without any connection with its 

 anterior lip. 



Text-fie-. 198. 



Esox lucius. 

 Diagram of olfactory organ in longitudinal section. 



A description of this cavity is given by Blaue. 



The organ lies well above the range of any pressure that might 

 be caused by the swelling of the adductor mandibular, but probably 

 currents of water are deflected into the cavity of the chamber 

 during forward progression by the tilt of the nostrils towards the 

 front and by the downward bend of the bridge between the two 

 nostrils. 



SCOPELID^. 



Scopelus crocodilus. 



The nostrils are simple circular perforations in a smooth area 

 of skin lying as usual between the lachrymal and nasal scutes. 

 The posterior is four times as lai-ge as the anterior and is separated 

 from it by a narrow bridge of integument. 



The olfactory chamber is globular and lies partly within the 

 iisual hollow in the ethmoid cartilage, but extends also over the 

 maxillary process of the palatine and the head of the maxilla. 

 This somewhat abnormal position is due to the extreme antero- 

 posterior compression of the front part of the face. 



The lining membrane of the chamber is deeply pigmented 

 except upon the rosette, which is brilliantly white in contrast . 



The rosette is of very unusual form (text-fig. 199, A), being 

 linear with its axis lying in the plane of the two nostrils. It is, 

 however, composed as usual of a series of laminfe arranged along 

 the sides and around the posterior end of an elongated central 



