244 The Commercial Products of tite Sea. 



it will repel the edge of a sharp knife when applied to it. 

 These bladders, when perfectly dried, vary in weight from 

 half to three-quarters of a pound avoirdupois. This fish 

 abounds in Channel Creek, off Saugor, and in the mouths 

 of all the rivers which intersect the Sunderbunds they are 

 exceedingly plentiful in certain seasons. 



The discovery of isinglass as a product of India was so 

 important that Dr. Cantor determined to investigate the 

 subject, and to ascertain what were the fishes which yielded 

 it. These seemed to be principally one or two species of 

 Polyjiemus, especially the Polynemus sele of Hamilton's 

 " Fishes of the Ganges," and the gol or gheriah (Corvinus 

 niger). P. sele is supposed by Royle to be a variety of 

 P lineatus, which is said to be common on all the shores 

 to the eastward. A larger species, P. tetradactylus, Shaw, 

 is also believed to furnish some of the Indian isinglass. 

 Several of the Siluridae also afford it in large quantities, espe- 

 cially the species marked Silurus raiia by Dr. Buchanan. 



The kinds of fishes from which this useful substance 

 has been obtained in India do not appear in all instances 

 to have been correctly defined, for it has been suggested 

 as derived from some which are destitute of air-vessels. 

 Without entering too minutely into the subject, it may be 

 stated that along the western coast, and down Malabar, the 

 Siluroids are in the majority; but wherever large rivers 

 debouch into the sea, there the Polynemi are captured. 

 As we advance up to the eastern coast, at first the Acan- 

 thopterygians are in excess, whilst off Masulipatam, to the 

 north again, the Polynemi become numerous, especially off 

 the Sunderbunds. In Burmah, due to the character of 

 the water, the Siluroids again obtain the predominance. 

 Amongst the isinglass-producing Acanthopterygians, the 

 Polynemi are most noted, but the species constituting this 



