ON THE ANATOlvrY OP FISHES. 
207 
downwards in contact with the lateral surface of the complex centrum, but is also 
prolonged slightly forwards to a pointed termination. 
Callichrous bimaculatus. 
The air-bladder, Weberian ossicles and skeletal modifications are precisely similar 
to those of C. ceylonensis. The intercalarium, however, consists of a hook-shaped 
process imbedded in the interossicular ligament and prolonged horizontally inwards 
as a slender spicule towards the membranous walls of the neural canal, thus forming 
a rudiment of the horizontal process of Macrones, but there is no trace of an 
ascending process. The body in the region of the lateral cutaneous areas is partially 
translucent. 
Callichrous paljo. 
This species is almost identical with the preceding in all points with which we are 
now concerned. 
Callichrous hypophthalmus. 
This species differs but little from the three preceding examples of the genus. 
The air-bladder is, however, less elongated and more cordate in shape, and, relatively 
to the size of the body, somewhat smaller. As in most other species of Callichrous, 
the lateral cutaneous areas are very thin and externally present the appearance of 
superficial blisters ; internally, they are closely applied to the lateral walls of the 
anterior chamber of the bladder. The extreme thinness and transparency of these 
areas, and their close relation to the thin-walled anterior chamber, combined with the 
laterally compressed shape of the fish, have the efiect of rendering this region of the 
body translucent when the animal is held up to the light. 
The intercalarium consists of a flattened nodule in the interossiciilar ligament, 
which is prolonged horizontally inwards as a slender spicule, and eventually terminates 
in the fibrous wall of the neural canal, dorsad to the anterior extremity of the 
complex centrum, and immediately behind the condylar process of the scaphium, but 
there is no trace of an ascending process. 
Shilhe mysius. 
With the exception of one or two minor features this African Slluroid is in close 
agreement with Callichrous ceylonensis, both as regards the condition of its air- 
bladder and the general character of the associated skeletal modifications. 
The air-bladder is less compressed than in the latter species, and, consequently, is 
relatively wider and not so deep. The primary transverse septum is thick but of 
somewhat greater transverse extent. Instea,d of being thin and tympaniform, the 
