648 MR. R, H. BURNE ON THE ANATOMY OF THE [May 25, 



The antei-ioi' nostril is tubular with the hinder lip raised to 

 form a narrow leaf -like appendage ; the posterior is a small circular 

 open hole. They are separated by a bridge of moderate breadth 

 (about three times the diameter of the posterior nostril). 



The rest of the nose diflfers somewhat on the two sides of the 

 head. On the right (ocular) side the olfactoiy chamber is broader 

 than long, and contains a correspondingly broad rosette, in which 

 the laminse, which are about twenty-five in number, lie longitudi- 

 nally and parallel to one another. The individual laminae have 

 a sharply angled free border. The hinder margin of the rosette 

 is attached by its middle to the posterioi- wall of the olfactory 

 chamber by the membranous fold that carries the olfactory 

 nerve, but on either side of this attachment it forms the free 

 anterior border of an oval hole that leads into an accessory sac. 

 The nasal sacs in form, position, and mode of connection with the 

 olfactory chamber resemble the ethmoidal and lachrymal sacs of 

 other Acanthopterygians (e. g. Pagelhts). The ethmoidal passes 

 upwards beneath the ethmo-maxillary ligament into the space 

 between the mesethmoid, the backward process of the premaxilla, 

 and the maxillary process of the palatine ; the lachrymal extends 

 downwards and forwards in a similar manner deep to the 

 lachrymal and the overhanging lachrymal process of the lateral 

 ethmoid to the hinder border of the maxilla, lying upon the 

 palatine bone and the buccal membrane. The sacs are compressed 

 by the movements of the premaxilla and maxilla in the closure of 

 the mouth. Upon the blind side the nose is essentially similar, 

 but owing to the rotation of the face the form and position of the 

 accessory sacs have become somewhat distorted. 



Both sacs lie above the maxillary process of the palatine, being 

 rotated forward on either side of the olfactory chamber, and lying 

 side by side in the hollow of the ethmoid that also lodges the 

 olfactory chamber. The ethmoidal sac is the larger of the two 

 and reaches the backward j)rocess of the premaxilla ; the lachrymal 

 sac terminates in front above the root of the maxillary process of 

 the palatine. 



Pleitronectes plaiessa. 



The olfactory organs of the Plaice are quite similar to those of 

 Hippoglossits* , except that the posterior nostrils are surrounded 

 by a thin upstanding valvular lip. Their topography has been 

 described in detail by Cole, if anything with too great elaboration, 

 for the accessory sacs are not strictly speaking subdivided into 

 the definite sacculations described by Cole, but are simple pear- 

 shaped bags fitting into the interstices between the difierent 

 bones with which they come in contact, and capable, when the 

 bones are stretched apart, of being completely smoothed out, 

 leaving no trace of permanent subdivision. 



* A rosette with longitudinally arranged laminae has been recorded (Bateson) for 

 three species of Fleuronecfes besides P. platessa. 



