AIR-BLADDEK IN NOTOPTERUS BOENEENSIS. 525 



special connection or physiological relationsliip with the auditory 

 organ. As regards the precise nature of the connection between 

 the two organs in different Pish6s, three principal methods may be 

 distinguished : — 



A. Auditory caeca are present, and the anterior extremity of 

 each is closely applied to a fontanelle in the outer wall of the 

 auditory capsule, the utricular portion of the membranous 

 labyrinth and the surrounding perilymph being in relation with 

 the inner surface of the fibrous membrane by which the fontanelle 

 is closed. In no part of their course are the auditory caeca 

 enclosed within bony canals or grooves, and no connection 

 between the auditory organs of opposite sides of the head has so 

 far been described. 



According to Stannius (11. p. 171) this method of connection 

 is characteristic of Briacantlius * macrophthalmus, C. & V. 

 (P. arenatus, C. & V., or P. cruentatus, C. & V. t), among the 

 Serranidse ; of certain species of Berycidse pertaining to the 

 .genera Myripristis and Holocentmm ; and possibly of JSyodoii 

 elaudulus (^H. tergisus, Les.), the solitary representative of the 

 North- American freshwater family of the Hyodontidae. Jeffery 

 Parker (8) has recorded an essentially similar arrangement in the 

 New Zealand Gradoid, Lotella (^PseudopJiycis) hacchus; and 

 Weber (12. pp. 71-72) for such Sparidse as Sparus salpa, Linn. 

 {Box salpa, C. & v.), and S. sargus, Linn. {Sargus Hondeletii, 

 C. & Y.). 



B. Instead of being closed by a fibrous membrane, the auditory 

 fontanelles are open, and through each of them passes a csecal 

 jdivertieulum from the corresponding utriculus, which thus 

 becomes directly and closely applied to the anterior extremity 

 of an auditory caecum. 



Those Teleosts which afford examples of this method of 

 connection by direct apposition are also characterized by certain 

 other noteworthy modifications. Thus, for the greater part of 

 its forward course each slender auditory caecum is enclosed in 

 bone, first traversing a groove and subsequently a canal in the ex- 

 occipital bone, and finally terminates by dividing into two distinct 

 vesicular enlargements, of which one lies in a chamber excavated 



* The generic name " Triaccmthtis" given by Stannius (loc.cit.) is apparently 

 a misprint for Friacanthus. 



t For synonyms of P. maorophthcdmus, vide Brit. Mus. Cat. Fishes, 2nd ed. 

 ^ol. i. p. 353 & p. 366. 



