620 



MR. K. H. BURXE ON THE ANATOMY OF THE [May 25, 



in the ethmoid cartilage, but its parts posterior to the rosette 

 ai-e extended beneath the three anterior scutes of the circum- 

 orbital ring, forming a laterally flattened accessory nasal sac pro- 

 longed above and below along the anterior contour of the orbit 

 (text-fig. 192, p. 619). This accessory sac is bounded by the orbital 

 ring externally, by the ethmoid and palatine bones and cartilages 

 internally, by the adipose eyelid posteriorly, and by a pad of 

 fat lying on the buccal membrane in front. When the maxilla 

 is retracted towards the eye the cavity of this sac is compressed 

 by the p'ad of fat. 



The rosette is attached to the floor of the olfactory chamber 

 directly beneath the nostrils, and is composed of from 12-14 

 transversely pleated claw-shaped laminae that radiate from a 

 short central raphe attached anteriorly to the front wall of the 

 anterior nostril. 



The posterior laminae of the series are far larger than the 

 others and project freely into the posterior nostril. 



Osmerus eperlamos. 



The olfactory organ is in all essential points similar to that 

 of the Salmon, but when the movith was closed forcibly under 

 water no air bubbles escaped fi'om the nostril, as might have 

 been expected from the form and position of the accessoiy 

 cavities. 



Coregonus oxyrhyiichus. 



The olfactory organ is essentially similar to that of the Salmon. 



Text-fiir. 193. 



Coregonus oxyrhynelms. 

 Diagram of nostrils, olfactory chamber, and nasal sac in longitudina section. 



V.j^valve. 



The anterior nostril is, however, surrounded by an upstanding 



