ON THE ANATOMY OF FISHES. 
213 
without completely filling the latter, or extending as far as the external skin, while 
its anterior and antero-lateral margins are supported by the inferior limb of the post- 
temporal. By these modifications the air-bladder becomes divided into two sy mm^etrical 
lateral compartments by a broad, solid, and continuous longitudinal partition. We 
could discover no trace of a ductus pneumaticus, or of any communication between 
the lateral cavities. A rudiment of a transverse septum (^.s.) partially subdivides each 
cavity into a relatively large anterior moiety, and a very small posterior chamber, 
which intercommunicate round the free outer edge of the septum, and may be 
compared, the former to the lateral half of an anterior chamber, and the latter to a 
rudimentary lateral compartment. The transverse septum is continuous mesially 
with the thick longitudinal partition, and dorsally and ventrally with the correspond- 
ing walls of the bladder. The dorsal edge of the septum is firmly attached to the 
posterior margin of the root of the transverse process of the fourth vertebra. 
Notwithstanding its small size and partial encapsulation by bone, the air-bladder has 
extremely thick walls, composed of densely matted fibres, in which, for the most part 
no very definite arrangement can be made out. Nevertheless, in the comparatively 
thin anterior portion of the dorsal wall radially arranged (in.st.) and curvilinear 
fibres may be seen, which here, as in the normal Siluridae, converge from the anterior 
and antero-lateral walls of each half of the bladder to their insertion into the 
crescentic process of the tripus (tr.c.). Radial fibres may also be seen converging 
from the inner margin of the crescentic process, and from its ventral ridge, towards 
the lateral surface of the complex centrum, to which they appear to be directly 
attached without the intervention of a radial nodule. 
The scaphium has no ascending process, but is otherwise normal, and its spatulate 
process has the usual relations to the external atrial aperture of its side. The inter- 
calarium is a small osseous nodule in the interossicular ligament. The crescentic 
process of the tripus {tr.c.) occupies its normal position imbedded in the antero- 
internal portion of the dorsal wall of each half of the bladder, but has a very unusual 
shape. Instead of being curved, as in most Siluridae, the process is short and broad, 
somewhat triangular in outline, with the apex directed backwards. The converging 
fibres of the dorsal wall of the bladder are inserted into a longitudinal ridge on the 
ventral surface of the process ; anteriorly, this ridge is continued forwards to a point 
near the origin of the articular process, and there receives the insertion of the usual 
slip of fibres derived from the mesial portion of the corresponding lateral half of the 
anterior wall of the bladder. The claustra are unusually well developed, and rest by 
their expanded bases on the dorso-lateral margins of the body of the first vertebra. 
La'is hexanema. 
This Siluroid so closely resembles Cryptopterus limpok as regards the shape, 
structure, and skeletal relations of its air-bladder, that no special description of the 
