ON THE ANATOMY OF PISHES. 
IZ7 
broader than any that follow, and partially confluent at its root with the preceding 
process. The transverse processes of the sixth vertebra carry the first pair of ribs 
and are quite free. 
The radial nodule {r.n.) is a somewhat elongated ossification, loosely attached by 
fibrous tissue to the lateral surface of the complex centrum, and by the same means 
connected also with the slender dorsal lamina {d.l.), which, after passing beneath the 
posterior cardinal vein blends with the ventral surface of the transverse process 
of the fourth vertebra. 
The air-bladder (fig. 44 ) has no extrinsic muscles comparable to the compressor and 
tensor tripodis muscles of the South American PimelodincB. Its walls are fairly thick, 
and its lateral compartments devoid of any trace of secondary transverse septa. The 
primary transverse septum {t.s.) stretches completely across the bladder, but two 
large circular apertiures place the anterior and lateral compartments in free com- 
munication with one another. The skeletal attachments of the anterior wall are 
similar to those of Platy stoma, except that the median portion of its outer stratum is 
firmly attached to and supported by the fan-shaped sub-vertebral processes. The 
attachments of the converging fibres of the antero-lateral, lateral, and dorsal walls 
of the anterior chamber to the tripodes are normal. Fig. 44 shows the outer stratum 
of the tunica externa of the anterior wall {o.st.), and incidentally also, the lateral 
peritoneal cul-de-sacs (p.c.s.), in which the small lateral lobes of the liver are lodged, the 
recesses which contained the anterior lymphoid lobes of the mesonephros {mph.r.), and 
the aponeurotic membrane bounding these recesses anteriorly and dorsally {ap.m.). 
The Weberian ossicles require no special description. The anterior process of the 
tripus (fig. 43 , tr.a.) is very broad in proportion to its length, and has its anterior 
extremity greatly thickened for the attachment of the stout interossicular ligament. 
The crescentic process (figs. 43 , 44 , tr.c.) is rather stout, with a relatively slight and 
somewhat open curvature, and a decurved inner extremity. The intercalarium is a 
stout nodule in the interossicular ligament. The scaphium has a comparatively small 
spatulate process. 
The more noteworthy features in which Auchenoglanis differs from the majority of 
other normal Pimelodince are (a) the restricted extent of the superficial ossifications, 
which consequently fail to extend laterally on to the modified transverse processes, or 
ventrally round the dorsal aorta, so that the channels both for the dorsal aorta and 
the posterior cardinal veins remain as open grooves, instead of complete bony canals ; 
(6) the presence of paired sub-vertebral processes for the suppoid and attachment of 
the anterior wall of the bladder ; (c) the absence of lateral ca3cal outgrowths, of 
secondary transverse septa, and of compressor or tensor tripodis muscles. 
