206 
PROFESSORS T. W. BRIDGE AND A. C. HADDON 
Callichrous ceylonensis. 
This Siluroid bears a general resemblance to Wallago and Silurus in the structure 
of its air-bladder and skeleton, but some of the minor osteological details in which it 
differs from them indicate an approach to the J\Iacro7ies type — a tendency which is, 
perhaps, better marked in some of the other species of the genus. 
The body of the first vertebra is exceptionally well developed, being nearly as large 
as any of tlie normal centra tliat succeed the fifth. A pair of stout accessory articular 
processes are developed on its ventral surface for articulation with similarly situated 
processes on the contiguous margins of the complex centrum and basioccipital. The 
centra of the complex and fifth vertebrae are also of somewhat unusual length, that 
belonging to the “ complex ” being about a third the longer of the two, and both are 
much compressed laterally. 
The anterior division of the transverse process of the fourth vertebra is much 
stouter than the posterior ; towards its distal extremity the former carries a concave 
facet for articulation with the post-temporal, and is then strongly decurved and pro- 
longed into a rudiment of the characteristic crescentic process of Macrones and its 
allies. The transverse process of the fifth vertebra is quite distinct from the fore- 
going, and about equal in size to the normal processes which succeed it ; a slender rib 
is attached to its distal extremity. It will be noticed that it is the fifth, and not the 
sixth, vertebra, as in most other Siluridm, which carries the first pair of ribs. 
The superficial ossifications are but feebly developed, and can scarcely be said to 
appreciably thicken the lateral surfaces of the complex and fifth vej’tebral centra. 
Each ossification is interrupted by an irregular wavy suture as it extends over the 
junction of the two centra. There is a deep groove for the reception of the dorsal 
aorta. Anteriorly the ossifications thicken somewhat, and appear to terminate in the 
accessory articular processes of the complex centrum. A slightly elongated radial 
nodule is suturally attached to each side of the complex centrum, and to a prominence 
on its dorsal extremity the radial fibres of the trIpus are attached. In connection 
with the thickened dorsal end of the nodule there is a thin spicule-like dorsal lamina 
having the usual relations to the cardinal groove and the transverse process of the 
fourth vertebra. There is no proper sub vertebral process. 
The inferior processes of the post-temporals have no trace of post-temporal plates. 
The air-bladder is almost an exact counterjjart of that of W allago, and, in corre- 
lation with the laterally compressed shape of the body, is narrow, but unusually deep. 
The lateral walls of its anterior chamber are in close and extensive contact with 
the lateral cutaneous areas. In the extent and nature of the skeletal attachments of 
its air-bladder this genus closely agrees with Macrones. 
The Weberian ossicles very closely resemble those of Cnidoglanis. The posterior 
and inwardly directed portion of the crescentic process of the tripus is not only bent 
