Sisor. GANGETIC FISHES. 207 



They leave exposed their membranes, each containing fourteen 

 rays. There is a slit under the throat. 



The declivity of the shoulders is small. The sides slope out- 

 ward. There is a small bony plate before the back fin. The 

 shoulder-bones are visible. The form of the muscles is discern- 

 ible through the skin. The lateral lines slope a little down- 

 ward, and are straight. The vent is behind the middle. 



The foremost dorsal fin slopes behind. Its first ray is a very 

 short bone ; the second is a prickle, smooth on the edges, and 

 pointed by a substance like whalebone ; the others are branch- 

 ed. The hinder fin is much longer than that behind the 

 vent, and its edge forms an arch, rising highest behind. The 

 pectoral fins are very low, shorter than the head, and sharp 

 above. Each has eleven rays, of which the first is a strong 

 prickle, indented behind, and ending in a substance like whale- 

 bone ; the others are branched. The ventral fins are nearly as 

 large as the pectorals, and each has six rays, of which the first 

 is undivided. The fin behind the vent slopes quickly for- 

 ward from the fourth ray, and slowly backward, and its three 

 first rays are undivided. The lobes of the tail fin are sharp, 

 and the upper is by much the longest and most pointed, and is 

 bent in form of a sickle. In all, the fin has seventeen distinct 

 rays, besides several compacted ones on each side. 



IX. Genus. — Sisor. 



Fishes of the fifth order, with a slimy skin, destitute of 

 scales or plates on the side of the tail ; with the mouth sur- 

 rounded by tendrils ; and with two fins on the back, the hin- 

 der one having one ray. 



The Cataphractus of La Cepede differs in having bony plates 

 on each side of the tail. 



