630 



ME. R. H. BURXE ON THE ANATOMY OF THE [May 25, 



raphe. The individual laminpe (text-fig. 199, B) are very small, 

 especially in the length of their attached base, and are acutely 

 pointed. 



Text-fig. 199. 



PN. 



A. OR. 



Scopelus erocodihis. 



A. Position and form of nostrils and olfactory ehamber. 



B. Diagram of the lamiiipe of the rosette. 



Cyprinodontid^e. 

 Anableps microle2ns. 



The posterior nostril lies just in front of the lower part of the 

 eye. It is a vertical slit, and is apparently valved against ingress 

 by the thinness and flexibility of its posterior lip. The anterior 

 nostril lies at the end of a short tube overhanging the edge of the 

 maxilla about its centre (text-fig. 200, A). Forcible closure of 

 the mouth under water caused air within the nose-cavity to bubble 

 from the posterior nostril, indicating the presence of accessory 

 sacs in connection with the olfactory chamber. Dissection shows 

 that the nasal cavity is in fact separable into two parts — one just 

 within the anterior nostril occupied by a simple oval rosette, and 

 thus the olfactory chamber proper, and another between this 

 and the posterior nostril lined by smooth membrane and extending 

 forward deep to the rosette across the maxillary process of the 

 palatine and beneath the maxilla to the hinder edge of the pre- 

 maxilla. This second portion of the cavity is an accessory nasal 

 sac whose state of compression depends upon the movements of the 

 premaxilla, and acts as an aspirating mechanism for the production 

 of water currents in the nose-cavity. The action of the jaws when 



