ON THE ANATOMY OF FISHES. 
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Pangasius djambal. 
In all osteological details (fig. 90) this Species is practically identical with 
P. Buchanani, but in the structure of the air-bladder the former presents one or 
two minor points of divergence from the latter. 
The air-bladder of P. djambal (fig. 93) consists of an anterior portion subdivided 
in the usual way into an anterior (a.c.) and two lateral (l.c.) compartments, and also 
of a posterior csecal appendage (p.c.). The latter is not tubular, as in P. buchanani, 
but has the shape of an elongated, flattened, oval structure, and extends nearly to 
the hinder extremity of the abdominal cavity, being separated from the rest of the 
bladder anteriorly by a deep constriction ; from its posterior end a small csecal 
protuberance {p.c?) is given off, which is less than half an inch in length, and 
gradually tapers to a point near the anus. The cavity of the csecal appendage (p.c.) 
is largely filled up by a network of fibrous bundles, some of which are vertically 
and others horizontally arranged, the whole forming a coarse trabecular structure 
and subdividing the cavity into a series of intercommunicating spaces. The network 
seems to owe its formation to the disintegration of a median longitudinal septum and 
several secondary transverse septa. In a somewhat similar fashion the longitudinal 
septum {I.S.), and the secondary transverse septa {t.s?) of the two lateral compart- 
ments are broken up into a series of not very regularly arranged vertical columns, 
which dorsally and ventrally pay out into root-like bundles and extend into the 
adjacent dorsal and ventral walls. As far as the tunica externa is concerned these 
septa are certainly not continuous structures, and hence the spaces they enclose 
appear to be in direct and free communication with one another. It is possible, 
however, that the tunica interna may preserve the continuity of the septal elements 
and the distinctness of the lateral chambers, except of course where the latter are 
continuous through the anterior chamber, but we are not absolutely certain on this 
point. Except where the oval plates of the “elastic-spring” mechanism {t.p.'^a.) are 
applied to the lateral regions of the anterior wall of the bladder, the latter organ has 
much thicker walls than is the case with any of the other species of Pangasius 
that we examined. Fig. 94 represents the tripus of this specimen. 
Pangasius macronema. 
This species exhibits a general resemblance to the two preceding species in the 
structure of the air-bladder and the character of its “elastic-spring” apparatus. 
The anterior division of each of the modified transverse processes has a slender stalk- 
like root, which, after a very slight ventral curvature, expands into a large but very 
thin oval plate. Each plate has its long axis transversely disposed, and its posterior 
face, which looks directly backwards, is closely applied to the corresponding lateral 
half of the anterior wall of the air-bladder. 
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