182 
PROFESSORS T. W. BRIDGE AJID A. C. HADDO?! 
the complex vertebra with the basioccipitnl, it is clear that nothing comparable to the 
singular for\^'ard dislocation of the anterior vertebrae through the foramen magnum 
and into the cranial cavity, which is so remarkable a feature in Hypophfhalmns, 
takes place in Loricaria. The bony capsules for the air-bladder are formed by the 
transverse process of the fourth vertebra in conjunction with certain of the bones 
forming the posterior face of the skull, viz., the posterior plates of the exoccipitals, 
the epiotics, and possibly the pterotics, in much the same fashion as in TlypophtJinlmiis, 
except that the post-temporals form the external walls of fhe capsules and more or less 
completely close their terminal apertures. 
As in Acantliicus the sacculi occupy shallow depressions in the cranial surface of 
the basioccipital, separated by a faint median ridge. It is possible that these struc- 
tures may have a fibrous roof, but it is certain that they are not invested dorsally by 
horizontally disposed bony plates derived from the two exoccipitals. We could not 
with certainty localize the position of the cavum sinus imparis and its atria, but they 
are probably situated on the dorsal surface of the basioccipital, between the depres- 
sions for the sacculi anteriorly, and the apertures Avhereby the anterior extremities of 
the tripodes enter the neural canal posteriorly. In that position, and as in Acantliicus, 
there is a slight median depression, which divides behind into two short inconspicuous 
grooves leading towards the apertures in question, and may possibly indicate the posi- 
tion of these cavities, but if such be the case their walls must be largely fibrous. The 
scaphia and the anterior extremities of the tripodes project freely into the occipital 
portion of the cranial cavity, and from the position of the former ossicles it is clear 
that the external atrial apertures must also be within the cranial cavity, as is the 
case with such other abnormal Siluridae as, for example, Callomystax. The condition 
of our specimen was fatal to a satisfactory examination of the internal ear. We were 
able to ascertain that a very short ductus endolymphaticus is present, but whether a 
sinus endolymphaticus is present or absent we cannot with certainty say. 
The air-bladder has extremely thin but structurally perfect walls. Each lateral 
air-sac is confined to the more dilated proximal portion of its bony capsule, which, as 
Rei.ssner states, is separated from the distal portion by a slight transverse ridge.* 
Apart from their cojmection with the tripodes, which appears to be perfectly normal, 
the walls of the air-sacs are free from any special attachments to the skeleton or to 
the inner surfaces of their bony capsules. There is no doubt as to the existence of a 
connection between the two sacs by means of an extremely slender, thin-walled 
intermediate canal, which leaves each capsule at the point indicated by Retssner. 
The articular process of the trlpus is situated at the point of junction of the 
anterior and posterior processes, which, as Reissner states, are united at a right 
angle. Neither claustra nor intercalaria could be detected. 
* In onr specimen ench sac was about 3 inm. in lengtli and in width, tlio length of the Fisli being 
7 inches. 
