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PROFESSORS T. W. BRIDGE AND A. C. HADDON 
relations of its component fibres to the tripus, each air-sac is strictly comparable to 
the lateral half of an anterior chamber in a normal bladder. The posterior wall 
of the intermediate tubular portion and the adjacent inner portion of the posterior 
wall of each sac are continuously thickened by the development of a thick mass of 
vertically disposed fibres (fig. 40, jp.jp.). On the ventral surface of the hinder part 
of the complex centrum these fibres separate into two bundles which pass dorsally 
one on each side of the centrum, and ultimately after curving slightly forwards 
become firmly inserted by their dorsal edges into the lateral surfaces of the complex 
centrum, and into the posterior margins of the dorsal laminae (fig. 39, d.l.). It is 
evident that these skeletally attached fibres almost precisely resemble the posterior 
pillars of a normal anterior chamber. In addition, tbe anterior wall of each air-sac is 
attached to the anterior margin of the modified transverse process by a superficial 
stratum of fibres which separates from the rest of the wall and is inserted into the 
process in question. More internally the same stratum is attached to the lateral 
surface of the complex centrum and to the corresponding dorsal lamina. The cres- 
centic process of each tripus (fig. 40, tr.c.) is imbedded in the dorsal wall of the 
contiguous air-sac, near the antero-internal angle of the latter. The relations of the 
process to the principal sheets of fibres in the dorsal wall appear to be perfectly 
normal. Thus, the fibres constituting the inner stratum of the mesial part of the 
anterior wall have the usual insertion into the radial nodule and ventral surface of the 
tripus, but from this point outwards the fibres forming the inner stratum, as well as 
those of both the inner and outer strata of the lateral wall, and the outer portion 
of the posterior wall of each sac, extend into the dorsal wall and finally converge to 
their insertion into the convexity of the crescentic process (fig. 40). It will be 
obvious, therefore, that but for the insertion of the fibres of the inner stratum of the 
tunica externa of the lateral and dorsal walls of each air-sac directly into the tripus 
the skeletal attachments of the anterior and lateral walls are almost precisely the 
same as in the anterior chamber of Platystoraa and other Pimelodinm with normal 
bladders. 
The most interesting feature in connection with the air-bladder of this species 
is, that while its small size and partial constriction into two lateral air-sacs would 
suggest that it represents an incipient stage in the kind of retrogressive modification 
of which Bagarius and Glyptosternum are extreme examples, it nevertheless retains 
its normal attachments both to rigid portions of the skeleton and to the tripodes, as 
well as the structural integrity of its walls, and the usual connection with the 
alimentary canal. 
The ventral surfaces of the two air-sacs are invested by an unusually large 
mesonephros, which also extends laterally and, in conjunction with the peritoneal 
hepatic pouches and their contents, separates each sac from the adjacent lateral 
cutaneous area. The mesonephros of the right side only accompanies the correspond- 
ing posterior cardinal vein to join its anterior lymphoid portion. The latter part of 
