Parker. — On the Red Cod (Lotella bacchus). 235 



Bather more than two years ago* a paper was read before the Zoological 

 Society of London, by Professors Bridge and Haddon, on the auditory os- 

 sicles of fishes ; I was unfortunately unable to hear the paper read and as 

 far as I know it has not yet been published, but before I left England Mr. 

 Haddon was good enough to give me a verbal account of the chief results 

 contained in it. One of these was that in many fishes, notably certain 

 Siluroids, the processes of the air-bladder were produced outwards to the 

 side- walls of the body, where the skin became very thin, forming a sort of 

 tympanic membrane, the vibrations of which were transmitted through 

 the air-bladder to the ossicula-auditus and thence to the organ of 

 hearing. 



On dissecting the common Bed Cod a short time since, I was interested 

 to find a combination of the two arrangements jnst described. As no ac- 

 cessory auditory apparatus has, I believe, hitherto been described in any of 

 the Gadidm, I have thought it advisable to present the following account to 

 the Institute. 



On the hinder surface of a roughly-prepared skull of Lotella, there is on 

 each side of the occipital condyle (fig. 1, ox) a large foramen (au.f), bounded 

 internally by the basi- and ex-occipitals (b.o, e.o), and externally by the opis- 

 thotic (ojj.o). If the skull is prepared with sufficient care, this foramen is 

 seen to be filled with an extremely thin plate (Z), formed partly of bone, 

 partly of membrane : its inner half is strongly plaited and fan-like, and 

 belongs to the basi-occipital : it is separated by a membranous interval 

 from the outer half, which is formed by the opisthotic, and is nearly smooth. 

 This lamina forms the lower part of the posterior wall of the auditory cap- 

 sule : the foramen, with the lamina stretched across it, may be called the 

 auditory fontanelle. 



Immediately below and internal to this fontanelle is a large downwardly 

 directed process (x) of the basi-occipital, serving for the attachment of some 

 of the neck muscles, and having its hinder surface concave : immediately 

 external to the fontanelle is a process of the opisthotic [y) also bearing a 

 concave surface : and external to this again on the posterior surface of the 

 parotic process is a third facet (z) furnished by the pterotic. 



The walls of the air-bladder (fig. 2) are for the most part thick and 

 tough, but on the anterior half of its dorsal surface they become so thin as 

 to be hardly distinguishable from the periosteum of the vertebral column. 

 Near its anterior end the bladder becomes markedly constricted, and in 

 front of the neck thus formed dilates considerably, forming the cornua 

 which pass outwards and slightly forwards and upwards with this anterior 



* In the early part of 1880, I believe ; but strangely enough I can find no notice of 

 the paper in the Index of " Nature." 



