ON THE AIR-BLADUER IX IS^OTOPTERUS. 503 



Fig. 2. The form referred to on p. 488 ; on one side of the specimen the pali 

 are developed, and ou the other the calicles are deep and the pali quite 

 obscured as a definite system. 



Fig. 3. A form with the more usual ring of five pali. Traces of the others and 

 of the columellar tubercle can be seen. 



Fig. 4. A leaf-like specimen of P. e.vilis, Gardiner, showing the directives all 

 pointing in the direction of growth (towards the top edge of the 

 figure). 



Fig. 5. A form with thin wavy walls and showing a double calicle ; the colu- 

 mellar tangle rises to the surface, and here and there unites the pali in 

 a ring. 



Fig. 6. A coenenchymatous form, the ccBnenchyma rising into rounded ridges 

 andpapillje ; the pali are slightly exsert and are often slightly V-shaped. 

 In a few cases the dirpctive principal and its adjacent lateral supple- 

 mentaries can be seen forming a very blunt broad arrow (the triple 

 fusion mentioned on p. 490). 



The Air-bladder and its Connection with the Auditory Organ 

 in Notopterus botmeensis. By Prof. T. W. Bridge, Sc.D., 

 i\L.S., Mason University College, Birmingliam. 



[Read 21st December, 1899.] 



(Plates 36 & 37.) j 



Contents. 



Page 

 i. Introdnction , 503 



ii. General Structure and Relations of the Air-bladder 504 



iii. Internal Structure, and the Relations and Attachments of the Air- 

 bladder to the Skeleton 507 



iv. Relations of the Air-bladder to the Skull and Auditory Organs 513 



V. Cranial Fontanelles and their Relation to the Auditory Oi'gan 516 



vi. The Auditory Organ 518 



vii. Comparison with Notopterus Pallasii , ,,... 519 



viii. Comparison with other Teleosts 522 



ix. Remarks on the supposed Auditory Function of the Air-bladder 531 



X. Bibliography 538 



xi. Explanation of the Plates, Reference-letters 539 



I. iNTHODTJCTIOlSr. 



While recently dissecting the air-bladder and associated struc- 

 tures in a specimea of Notopterus horneensis, Bleaker, certain 

 features were noticed in which this species differed from Noto- 

 pterus Pallasii^ C. & V., as described by Cuvier and Valenciennes 

 (4. pp. 139-141), How far the differences observed are due to 



38* 



