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



enterirg thi-ough the anterior nostril into the heart of the 

 rosette. 



The olfactory chamber occupies a similar position relative to 

 the bones of the skull, as in the Haddock, but slightly lower down, 

 so that its lower border rests upon the retractor of the maxilla 

 (text-fig. 191, p. 617). Its anterior part, ventral to the rosette, is 

 produced forward to form an accessory sac that passing forward 

 deep to the dorsal parts of the lachrymal bone dips beneath the 

 maxillary process of the palatine into the space included between 

 this bone, the head of the maxilla, and the vomer. 



The cavity of the olfactory chamber and accessory nasal sac 

 was filled with an unusually large amount of mucus. Apart from 

 a mucus-secreting function, it seems highly probable from its 

 position that this nasal sac would act as an aspirator bulb, being 

 compressed both by the movements of the head of the maxilla 

 and by the swelling of the jaw muscles upon and near which it 

 lies. This action must, however, be slight at the best, for no 

 bubbles escaped from the nostrils when the jaws were forcibly 

 closed under water. 



The rosette is cii'cular and is composed of about 28 laminae, 

 each of which is transversely pleated and has a claw-like outline 

 due apparently to an exaggeration of the linguiform process and 

 the almost complete suppression of the peripheral segment. 



Stbmmary. 



In the Anacanthini examined (Gadidfe) the olfactory organ 

 is of a simple type and shows great uniformity. It is, in brief, 

 a hemispherical depression, opening to the exterior by two 

 nostrils and containing a rosette of laminae for the lodgement 

 of the olfactory epithelium through which a current of water is 

 deflected during forward locomotion by an upstanding flap upon 

 the hinder border of the anterior nostril. The Hake stands 

 apart from the other examples not only on account of its nostrils 

 and rosette which are of a difierent, somewhat Salmonid, type, 

 but also by the possession of a well developed nasal sac accessory 

 to the true olfactory chamber. The modifications in the Rockling 

 are of minor importance brought about apparently by changes 

 extei-nal to the olfactory organ rather than in that organ itself. 



Malacopterygii. 



Salmonid^. 

 Sahno salar. 



The nostrils lie close together (text-fig. 192, A) upon a level with 

 the top of the eye and about halfway between it and the snout — 

 the posterior in close connection with the central of the three 

 anterior circum-orbital scutes. Both are elongated dorso-ventrally, 

 the anterior being a narrow slit, the posterior more oval. The 



