ON THE ANATOMY OF FISHES. 
191 
the neural canal, as well as in the peripheral distribution of the nerves themselves, 
Clarias agi’ees very closely with Macrones (fig. 79). 
The post-temporal has only a vestige of an inferior limb (fig. 78, which is 
firmly applied to the distal portion of the anterior wall of the bony funnel of its side, 
but remains widely separated from the basioccipital {h.o.). The expanded stem of the 
bone (p^-s.) is directly continuous with the ascending process (pt.a.), and is also 
traversed on its inner surface by a groove {cl.s.) for articulation with the proximal 
extremity of the clavicle. A backwardly projecting process from the stem (pt.s.) is 
closely applied to the distal extremity of the transverse process of the fourth vertebra 
in such a way as to encircle the anterior and dorsal lips of the distal a])erture of the 
funnel, the dorsal wall of which is also slightly lengthened, but without in any way 
closing or diminishing the size of the terminal aperture. Between this process and 
the outer margin of the roof of the funnel there is a foramen for the transmission of 
the lateral-line branch of the tenth cranial nerve as it passes backwards from the 
skull after traversing the dorsal surface of the funnel (x.). 
The cavum sinus imparis (fig. 79, c.s.i.), the fovese sacculi (f.s.), and the atrial 
cavities and their external apertures {at. a.) differ in no essential feature, either as 
regards mode of formation, relative size, or mutual relations, from the corresponding 
structures in Macrones, or any other normal Siluroid. 
Before dealing with the structure of the air-bladder brief reference may be made 
to certain investing membranes and other structures which are closely related to its 
osseous capsules. 
As originally stated by Taylor {loc. cit.), a thin but tough fibrous membrane 
completes the walls of the bony funnels w^herever vacuities exist between the 
modified transverse processes, or where they are otherwise incomplete, but is appa- 
rently restricted to the anterior ventral and posterior surfaces of the funnels. 
Mesially, the membrane extends across the ventral surface of the complex centrum 
and there furnishes a tubular investment to the contracted median portion of the 
air-bladder ; anteriorly, it is continuous with the walls of the saccus paravertebral! s 
(fig. 78, s.pv.), and apparently also, after extending forwards over the dorsal surface 
of the bilobed anterior extremity of the mesonephros, with the aponeurotic membrane 
separating the abdominal cavity from the pericardial and branchial cavities ; laterally 
the membrane extends over and closes the terminal apertures of the two funnels. 
The precise nature of this investing membrane is diflScult to determine. It may be 
merely a backward prolongation of the aponeurotic membrane over the funnels, or, as 
is perhaps more probable, the membrane represents what we have elsewhere regarded 
as the supeidicial fibrous coat of the air-bladder, and is indicated in the more normal 
Siluroids by the transverse membrane, or. In certain abnormal forms, e.g., Bagarius 
and Glyptosternum, by an external fibrous investment to the ventral surface of the 
rudimentary bladder. Whatever may be Its nature it is highly probable that the 
walls of the bony funnels are largely formed by the partial ossification of this 
