AlE-BLABDEB IN NOTOPTEEUS BOENEENSIS. 523 



inner walls of the caudal caeca reduced to so attenuated a condition 

 through the intimacy of their relations and attachments to the 

 caudal skeleton, as is the case in the last-mentioned species. Even 

 in the two species of Cryptopterus, where the caudal portion of 

 the air-bladder is in contact with the subvertebral hsemal arches 

 and spines, the walls of the organ are of uniform thickness and 

 are quite free from any special connection or attachment to the 

 skeleton. 



Perhaps, on the whole, the air-bladder of certain species of 

 Sparidse {e.g., species of Box) approaches more nearly to that of 

 Noptopterus than does the bladder of any other Teleosts. In 

 Box vulgaris, C. & V., not only are caudal cgeca present, but the 

 inner or mesial walls of these structures are devoid of an outer 

 fibrous coat, or tunica externa, and the tunica interna, which 

 alone remains, closely invests the opposite sides of the hsemal 

 arches and spines of the caudal vertebra^.. The resemblance is 

 further heightened by the fact that in Sparus salpa, L. {Box 

 salpa, C. & Y.), as Weber (12. p. 71 et seq.) pointed out, auditory 

 caeca are also present, although in the location of their connection 

 with the auditory fontanelles and in some minor details the 

 latter Sparoid does not precisely agree with Notopterus. On the 

 other hand, Box has no bifurcate ventral diverticula in connection 

 with the caudal caeca, and the air-bladder is wholly destitute of 

 internal septa, and of a ductus pneumaticus in the adult. 



The extension of the air-bladder into the tail in Notopterus, 

 as no doubt is also the case in many other Teleosts, is to be 

 associated with the extreme shortness and laterally-compressed 

 shape of the abdominal portion of the body, which, if the bladder 

 is to acquire its normal degree of development as a hydrostatic 

 organ, necessitates its prolongation into the caudal region *. 



In the disposition of the internal septa, and especially in the 

 development of a principal longitudinal septum which, anteriorly, 

 meets an incomplete transverse septum, the coelomic or abdominal 

 portion of the air-bladder of Notopterus presents some approxi- 

 mation to the characteristic T-shaped arrangement of the 

 primary septa in the bladder of a considerable number of 

 Siluroids ; and the resemblance is rendered still more marked by 

 the fact that in both the carinate shape of the suprajacent axial 

 skeleton involves a partial subdivision of the anterior portion of 

 the bladder through the inpushing of its dorsal wall in the 



* See reference to remarks by Giinther (7. footnote to p. 491). 



