ON THE AN'ATOMY OF FISHES. 
125 
anterior part of it, is closely adherent to the ventral and lateral surfaces of the 
complex centrum. We could discover no trace of a ductus pneumaticus unless a 
slender solid fibrous cord extending from the flattened median part of the bladder 
to the dorsal wall of the oesophagus may be regarded as a vestige of it. 
The mesonephros accompanies the right posterior cardinal vein through the cardinal 
canal, and at the anterior extremity of the latter expands into its usual lymphoid 
portion. The latter part of the gland surrounds the anterior extremity of the inner 
lateral caecum, and also the tubular portion of the outer lateral diverticulum, and, in 
addition, extends into the contracted median part of each flask-shaped recess. 
Except for its relatively small size the tripus is fairly normal (fig. 38, tr.). Com- 
pared with the anterior process (tr.a.) the crescentic section of the ossicle (tr.c.) is 
rather short, with a sharp hooked curvature. The articular process (tr.ar.) tapers to 
a point at its distal extremity. The crescentic process is imbedded in the dorsal wall 
of the anterior extremity of the inner lateral caecum. The convergence of the fibres 
of the inner stratum of the tunica externa to their insertion into the convexity of the 
crescentic process is very obvious, as also is the attachment of the concavity of the 
same process to the radial nodule by means of radial fibres, but the disposition of 
tlie usual curvilinear fibres of the outer stratum is not so easily traceable, although 
there is no doubt as to their insertion into the tripus. The intercalarium is a very 
small bony nodule in the interossicular ligament. Except that it has no ascending 
process the scaphium is normal. The claustra are slender spicular ossicles in the 
usual position. 
It need scarcely be added that there is no trace of compressor or tensor tripodis 
muscles. 
The cavum sinus imparis and the atrial cavities are normal, but we could not 
with certainty satisfy ourselves as to the presence or absence of a sinus endolym- 
phaticus. 
Callophysus mac ropterus. 
Under the name of Pimelodus macropterus, Johannes Muller (28, Plate 4, fig. 7) 
figures and briefly describes the air-bladder of this species. The organ is said to be 
small, heart-shaped, and flat, and to be surrounded along its sides and at the hinder 
end by an elegant wreath of small blindly ending diverticula. Anteriorly, where in 
Platystoma fasciatum a single pair of cmcal appendages is present, Muller found, on 
each side a very long, wide, blind diverticulum. 
Auchcnoglanis hiscnfatus. 
With one exception [Pimelodus platychir), Auchenoglanis is the only African repre* 
sentative of the essentially South American group of Pimelodina, and, in so far as its 
air-bladder and skeleton are concerned, has but little in common with the other 
normal members of the group. 
