360 Proceedings of the Royal Physical Society. 



is continued further back than the posterior margin of the anal fin. The 

 caudal fin is bifurcated, the superior half longer than the inferior. From 

 the longest ray above to the longest below, inclusive, there are seventeen 

 rays ; and outside these there are eleven shorter rays in each half. 

 There are thirteen rays in the anal, nine in the pectoral, and seven in 

 the ventral fin. The first pectoral fin ray in Synodontis is a large spine 

 toothed before and behind, the posterior teeth being longest, about equal 

 in length to the dorsal spine. There is no locking arrangement in its 

 joint, and therefore it can only be kept in the extended position by mus- 

 cular effort. On the other hand we find the lock-joint of the pectoral 

 spine in genera in which the dorsal spine is not fixed, as in this genus. 



The superior scute of the head passes back nearly as far as the third 

 dorsal fin ray. The coracoid scute is triangular, and passes back as far as 

 the superior scute. 



The long curved teeth which hang loosely in the lower lip, and which 

 give character to the genus, are twenty-four in number. Behind them 

 are fine velvety teeth, the patches of opposite sides distinct. In the 

 upper jaw there is a double row of conical teeth, about eighteen on each 

 side, and behind them (on each side) a patch of setose teeth of very 

 irregular size. 



There is one superior pair of barbules very long and simple, and two 

 inferior pairs, both of them branched, the outer pair half the length of 

 the superior pair, and the inner pair half the length of the outer. 



The specimen is twelve inches long from mouth to tip of tail, and three 

 inches from mouth to the first dorsal spine. 



A view of the swimming-bladder of Synodontis is given by Muller in 

 his work on Myxinoid fishes. 



3. Two of the specimens exhibited belong to the genus Clarias, which 

 is characterised by the presence of arborescent branchial appendages 

 attached to the second and fourth branchial arches, and by having only 

 one dorsal fin. 



The first of them corresponds exactly to one which I have had the 

 opportunity of examining in the British Museum, and which, therefore, 

 we may expect to have properly described by Dr Gunther in his elaborate 

 work, of which part is already published. The specimen is a foot long. 

 The head is depressed and shielded, oblong in form, the eyes small and 

 lateral ; the body is oblong, compressed. The dorsal fin extends from 

 within an inch behind the head back to the tail, but is not continuous with 

 the caudal fin ; it contains seventy- six rays, the first of which is not 

 spinous. 



The caudal fin contains twenty- four rays, the anal sixty-three, the 

 pectoral twelve, the ventral six. The first ray of the pectoral fin is a 

 spine toothed before and behind, and having a lock -joint, that is to say, 

 its joint is so constructed that when the spine is fully extended it cannot 

 be pushed back towards the body by any direct pressure, but must first 

 be rotated to a certain extent, and then it folds back easily. The anal 

 fin is continued, like the dorsal, back to the caudal, without being con- 

 tinuous with the latter. There is a papilla behind the anus. 



The teeth are velvety, in very broad patches. The teeth in the upper 

 jaw are larger than those in the lower ; the patch in the lower jaw is 

 broader than that in the upper, and indented at the outer side. On the 

 vomer there is also a broad patch of very minute teeth. 



The barbules are eight in number. The anterior superior pair are 

 longest, the external inferior pair slightly longer than the posterior 

 superior pair, while the internal inferior pair are thick, short, and trun- 

 cated, a character peculiar to this species. 



4. The other Clarias, which I exhibit, resembles two of the Indian 



