On East Indian Isinglass. 



187 



who reside on the spot to determine the nature of these discrepancies, 

 and whether they are owing to varieties, or to geographical position, 

 or to different species being confounded, from the want of means to 

 make direct comparison of those species of which the characters differ 

 but little. An Indian naturalist, who had only isolated descriptions 

 of many of our Cyprins, would be very liable to overlook those differ- 

 ences which we have found it difficult to seize when comparing nearly 

 allied species, and which our fishermen never mistake. But a confusion 

 of species, for which there is no excuse, is, that which was made by 

 Bruce, on the very species we are now describing. He has given in his 

 Travels, (Plate 41 ,) an exact figure from a drawing which appears to have 

 been made on the coasts of the Red Sea : but by one of those blunders 

 with which the work is replete, the name Binny is written at the bottom 

 of the plate, and if you refer to the text, you will find the true Binny 

 is a fish of the Nile, of the genus Barbus, (the Cyprinus binny, Forsk et 

 Gmel.) There is no Polynemus in the Nile, and on this extraordinary 

 mistake of Bruce, is founded the species Polynemus Niloticus of Shaw.* 



Our specimen from Pondicherry is a little shorter in proportion, the 

 head a little larger, and the second dorsal and the anal more pointed 

 than the Polynemus tetradactile, to which in other respects it bears a 

 close resemblance. The denticules of the preoperculum are also 

 smaller, and the inferior angle is round. The teeth are in straiter bands 

 and descend less outside of the lower jaw. Not only has it one ray 

 more, but the three first rays are longer than the pectoral, while in 

 the Tetradactylus, they are shorter. The ventrals are situated behind the 

 pectorals, and reach almost to the extremity of the free pectoral rays. 

 The lateral line extends in a line from the superior angle of the 

 operculum to the tail, on which it is prolonged a little downwards 

 with its slope. 



The number of its rays.— D. 8 : I a % : C. 17 : P. 17. v. \. 



" '1* 13 5 



Our specimen is silvery, with longitudinal grey or dark lines formed 

 rather by reflection than true tint, and prevailing along the whole of the 

 back to the tail. The fins are pointed and dark. M. Leschenault, to 

 whom we owe this specimen, and who saw it when fresh, assured us, 

 that the muzzle of the fish is transparent as gum ; and Commerson 

 also says so. In this state, the brown lines of the back are less ap- 

 parent, for M. Leschenault has described this species as grey on the 

 back and white below the belly. Commerson has given it only one 

 colour, a bluish silvery tint towards the back. The figure of Com- 



* Shaw, Univ. Zool. t. v. part 1st, p. 151. 



