208 
PROFESSORS T. W. BRIDGE AND A. C. HADDON 
longitudinal septum is unusually stout, being strengthened by the aggregation of its 
component fibres into vertically arranged column-like bundles. The lateral and 
antero-lateral walls of the anterior chamber are somewhat thinner than the rest of 
the bladder and in close contact with the external skin, but this region of the body 
is but feebly translucent. 
The Weberian ossicles also resemble those of Callichrous, except that the inter- 
calarium is a slender horizontally disposed spicule, one extremity of which is bifid and 
imbedded in the interossicular ligament, while the other ends in the fibrous wall of the 
neural canal at a point a little dorsad to the anterior margin of the complex centrum. 
Eutropius niloticus. 
This species differs but little from the preceding. Relatively to the size of the 
body, the air-bladder is perhaps somewhat smaller and has thicker walls, which are 
not perceptibly thinner in the lateral or antero-lateral regions than elsewhere, neither 
is the body in any degree translucent in the region of the lateral cutaneous areas. In 
shape the organ is obtusely conical and somewhat flattened, witli the broad end 
directed forwards. The intercalarium has a slender liorizontal 'process. 
Ailia hengalensis. 
In this interesting Indian Siluroid the air-bladder and the co-related parts of the 
skeleton exhibit very singular, and in some respects, unique modifications ; but the 
only reference to them with which we are acquainted is by Day (9), who very briefly 
described the air-bladder as being very similar to that of his new genus and species 
Ailiichthys j^unctata, in which the organ is said to be “ tubular, placed across the 
bodies of the anterior vertebrm, and more or less enclosed in bone” {he. cit., p. 713). 
The complex and fifth vei’tebrm are firmly united together by the anchylosis of their 
neural arches and spines, as well as through the continuity of the superficial ossifica- 
tions which invest the lateral surfaces of their respective centra. The sixth vertebra 
(figs. 87, 88, v.^) would be quite free but for the partial coalescence of the roots of its 
transverse processes with those belonging to the fifth vertebra, and carries the first 
pair of ribs. A deep aortic groove traverses the ventral surfiices of the complex and 
fifth vertebral centra. The spinous processes of third, fourth, and fifth vertebrae are 
confluent, and form a thin, vertical and somewhat elongated lamina of bone (fig. 88, 
91.5.^, n.s.^) ; anteriorly, the lamina has the usual articulation with the 
exoccipitals and supraoccipital. 
The transverse processes of the fourth and fifth vertebrae (figs. 87, 88, 
are greatly expanded and confluent, forming on each side of the vertebral column a 
broad wing-like outgrowth. The anterior margin of each outgrowth is bent downwards 
in close contact with the hinder face of the skull, and the posterior margin is similarly 
