ON THE ANATOMY OF FISHES. 
205 
removing the ventral wall it was apparent that the actual cavity of the bladder is 
even smaller than might be expected from its diminutive external appearance, inas- 
much as the posterior half of the organ, which probably represents the partially 
aborted lateral compartments, is occupied by a close network of anastomosing fibrous 
bundles. But so far as we were able to determine, and notwithstanding these indi- 
cations of degeneration, the general disposition of the fibres forming the walls of the 
anterior half of the bladder, and their relations to the axial skeleton and to the 
tripodes, are much the same as in the normal species of Cryptopterus. A ductus 
pneumaticus is present and communicates with the anterior section of the bladder. 
The crescentic process of the tripus has a rather open curvature, its posterior 
extremity being directed but slightly inwards towards the complex centrum. The 
intercalarium consists of an oblong nodule imbedded in the interossicular ligament, 
and in our specimen was continued internally into what appeared to be the fractured 
rudiment of a horizontal process. The scaphiuin is normal, having spatulate, con- 
dylar, and ascending processes. 
The cavum sinus imparis and the atrial cavities are normal, but we could arrive 
at no satisfactory conclusion as to the condition of the associated portions of the 
membranous labyrinth. 
Cryptopterus liexapterus. 
Except ill certain minor details the anterior vertebrae and their processes resemble 
those of C. micropus. As in the latter species the transverse processes of the fourth 
and fifth vertebrae are modified to form on each side of the complex centrum a shallow 
transversely disposed groove for the reception of the corresponding lateral half of the 
air-bladder (fig. 86). The anterior division of the transverse process of the fourth 
vertebra {t.p.'^a.) is shorter and thicker than in C. micropus, and, instead of being 
produced distally into a slender decurved portion, carries the articular facet for the 
post-temporal at its abruptly truncated extremity. The posterior division {t.p.^p.) is 
directed slightly backwards, and, in conjunction with the equally short and thick 
transverse process of the fifth vertebra, to which it is firmly applied, forms the 
posterior wall of the groove for the air-bladder. The first pair of ribs is carried by 
the sixth vertebra. We could detect no trace of a radial nodule or a dorsal lamina. 
The air-bladder is similar in shape and general structure to' that of C. micropus, but 
much smaller, its transverse extent being 5 mm., and its antero- posterior length 
2\5 mm., although in each case the specimens of the two species were of approximately 
equal length. Its walls are extremely thick, and laterally are widely separated from 
the superficial skin. The lateral halves of the bladder are in free communication with 
each other, and also with the central portion of the oesophagus by means of a ductus 
pneumaticus. 
The tripus and scaphiuin are also siriilar to those of the preceding species, and the 
intercalarium has a distinct horizontal j^rocess. 
