( 18 ) 



Ailitchlhys ; 17, Eatropiihthjs ; 18, Sisor ; 19, Oagata ; 20, 

 JJeniipimelodiin ; 21, But/uriuii ; 22, l^seiulecheneis ; 23, Olyp- 

 tosterimm ; 2d', Amblyccns, aud 2b, Exostoma. Out of the 

 foregoing 25 genera, soine are residents in waters of tlie 

 ])lains, also in rivers o^' the hills Avith or without Alpine 

 sources. A nougst the 5 7 resident solely in Avatcrs of tlie 

 plains, and not extendin;/ their range into hilly regions, we 

 find that in eight, Nos. ^, 3, 4, 5, 0, 7, 8, 9, the air-vessel 

 is free in the abdominai cavity and not enclosed in bone ; 

 whilst in ten, Nos. 12, lU, IX, 15, 16, 17, 18, 19, 20, 21, it is 

 more or less so enclosed. Amongst those residing in 

 rivers of the plains, anci extending their range into those 

 of the hills which have or are destitute of Alpine sources, we 

 perceive four, Nos. 22, 23, 21, 25, which are found in the 

 Avaters of the plains as well as in the hill rivers Avith Alpine 

 sources ; all have their air-vessels enclosed in bone, the 

 two first have a thoracic adliesive apparatus, whilst the last 

 three have representatives in the next division, and Nos 22 

 and 23 are furnished with a thoracic adhesive apparatus. 

 The remaining three genera, Nos. 1, 10, 11, are found in 

 rivers of the plains, and also in those of hills destitute of 

 Alpine sources, Avhilst in none is the air-vessel enclosed 

 in bone. From the foregoing it appears that the majority 

 of the genera of the Indian fresh-Avater siluroids have their 

 air-vessel enclosed in bone, whilst it is not so enclosed in any 

 of the marine forms; that amongst the siluroids of hilly 

 regions, those which ascend rivers having Alpine sources 

 liave the air-A^cssel enclosed in bone : Avhilst those Avhich 

 ascend rivers not snoAV-fed do not appear of necessity to 

 have their air-vessel thus protected. 



XXXI. The fresh-ioater siluroids may be divided 

 C-, ., (,.„ , ,. into those of tlie hills and those of 



Siluroids of Inlls aud i>luiu3. ,77- ji - 



the plains ; the jormer, or those ot the 

 hills, being small and often possessing a thoracic adhesive 

 apimratus to enable them to adhere to roclis, and prevent 

 tlieir being carried aAvay by descending torrents. The silii- 

 roids of the plains are very numerous, existing in almost 

 every piece of fresh-water, Avhilst the larger rivers contain 

 some, as the l\tn<jasius Ihichanaiii, JFallat/o utlu, Silundia 

 Ganyetica, and Bagariits Yarrellii, which attain to several feet 

 in length : in fact, up country, as in the upper portions of the 

 Jumna and Ganges and in the irrigation canals, Avliere they 

 find abundance of food, and consequently groAV to a very great 

 size, they are erroneously termed " sharks." None of these 

 siluroids possess any adhesive apparatus unless they are also 



