AIE-BLADDER IN" NOTOPTEET78 BORNEENSIS. 527 



two auditory capsules (sinus impar), is prolonged backwards to 

 its physiological connection with the most anterior of the series 

 of Weberian ossicles *. 



Wbether Syodon claudulus is rightly to be regarded as an 

 example of the first method, as stated above, or not, is by no' 

 means quite clear. The description of tbe connection between 

 the auditory organ and air-bladder in this Teleost, as given, by 

 Stannius {op. cit. p. 171), is as follows: — 



" Bei Syodon claudulus — und ganz analog verhiilt sich Noto- 

 pterus — communicirtdasvordere Ende desSchwimmblasenkorpers 

 durch enge Oeffnungen mit zwei spharischen dickwandigea 

 Blasen. Jede derselben legt sich in eine Yertiefuug der Knochen 

 der Hinterhauptsgegeud ihrer Seite und haftet eng an den 

 letzteren. Dem vordersten Theile jeder dieser Blasen entspricht 

 eine Oeffnung in den Knochen, die inwendig von einem Theile- 

 des Vestibulum, auswendig aber von der innersten Haut dieser 

 Blase bekleidet ist, indem die weisse Easerhaut derselben im 

 Umkreise der ausseren Gehorsoffnung aufhort und nicht iiber 

 letztere selbst sich fortsetzt." 



Erom this account it would seem that, as in the Clupeidse, the 

 auditory fontanelles in Syodon are not closed by fibrous mem- 

 branes, and, consequently, the auditory caeca, after losing their 

 outer fibrous coat, are either closely related to the vestibular 

 walls, or in actual contact therewith, or, at all events, are not 

 separated by any intervening fibrous membrane. If, however,, 

 the description given by Stannius is correct, then the statement 

 " und ganz analog verhalt sich Notopterus'''' is scarcely applicable 

 to that Teleost, inasmuch as there is no doubt as to the existence 

 of a separating membrane in Notopterus. 



It would be interesting to ascertain if any tubular communi- 

 cation between the two vestibuli, similar to that present in the 

 Clupeidse, exists also in Syodon. So far as I am aware, no 

 observations on this point have yet been made. 



Comparison of Notopterus with the various Teleosts mentioned 

 above, proves that it furnishes an additional example of the first 

 of the three methods by which the air-bladder and auditory organ 

 are brought into physiological relationsliip, although in one or 

 two minor features an approach to the second type is indicated. 



Thus in Notopterus there is no direct contact between the- 



* For references vide Bridge & Haddon (2. p. 65 et seq.). 



