172 
PROFESSORS T. W. BRIDGE AND A. C. HADDON 
fibres of the outer stratum pursue the normal curvilinear course in passing from the 
tripus into the dorsal, aritero-lateral, and lateral or outer walls ; the fibres of the inner 
stratum have exactly the same attachment and distribution, but radiate directly out- 
wards from the tripus. The two strata are of uniform thickness over the greater part 
of the dorsal wall of each sac, and together may be taken as representing one of the 
triangular sheets of a normal anterior chamber, but along a somewhat sharply defined 
line extending from the posterior or inner extremity of the crescentic process of the 
tripus, obliquely outwards and backwards to the outer margin of the posterior wall of 
the sac, the dorsal wall becomes extremely thin, resuming, however, its normal thickness 
as it subsequently extends downwards to form the posterior wall. This thin area 
probably corresponds to one half of the thin medio-dorsal portion of the tunica 
externa in a normal and undivided anterior chamber, and both it and the dorsal edge 
of the posterior wall appeared to be slightly adherent to the skeleton along an oblique 
line coincident with the posterior margin of the transverse process of the fourth 
vertebra. This adhesion of the posterior wall to the skeleton is evidently the 
equivalent of the dorsal attachment of the primary transverse septum in the normal 
bladder. The fibres forming the inner wall of each sac are attached dorsally to the 
feebly developed radial nodule, and, towards the anterior wall, to the ventral surface 
of the tripus near the root of its crescentic process ; these fibres represent what in 
other Siluroids we have termed the “ anterior pillars.” Radial fibres converge from 
the crescentic process to the radial nodule in the usual manner. 
The tripus occupies its normal position along the side of the complex centrum ; 
its anterior jjrocess, which is much the longest, is connected by a short interossicular 
ligament with the convex outer surface of the scaphium ; the articular process is very 
slender and directed obliquely backwards to an articular pit on the lateral surface of 
the complex centrum. Unlike most other abnormal Siluridae, the crescentic process 
retains its normal shape and curvature. For the terminal part of its course the 
process is bent downwards in contact with the side of the complex centrum ; the root 
of the process passes through a foramen at the antero-internal extremity of the 
osseous funnel, and anteriorly to the foramen gives off the articular process from its 
inner margin, and is then prolonged forwards as the anterior process. The scaphium 
consists of spatulate and condylar processes only, the ascending process being entirely 
suppressed. The spatulate process lies at the bottom of a deep notch in the posterior 
margin of the exoccipital and, as in GlyptosteriiuDi, projects so much inwards as to 
lie on the dorsal surface of the basioccipital within the cranial cavity. The inter- 
calarium is a minute nodule of bone imbedded in the interossicular ligament. We 
could detect no trace of claustra. 
The cavum sinus imparis and its atrial diverticula are certainly normal, and we had 
no difficulty in detecting a tranversely disposed ductus endolymphaticus, but we 
were unable to arrive at any satisfactory conclusion as to the presence or absence of 
a sinus endolymphaticus. 
