22 SECOND YARKAND MISSION. 



of the Himalayas, and sometimes even descending to the plains. Diptychus, Tibet, Ydrkand 

 and Western Turkestan. Schizopygopsis, Tibet and Yarkand. Ptychobarbus, Tibet and 

 Yarkand. The remainder are Loaches. 



Diptychus Dybowskii, Kess., would almost seem to be a Schizoijygopsisvriih an articulat- 

 ed dorsal ray and a pair of maxillary barbels. Perhaps several of these hill- genera will, at 

 some future date, be properly amalgamated, as has been done with the low-country Barbels 

 (Barbus). 



An examination of the genera of spiny-rayed or Acanthopterygian fishes clearly shows 

 that as we proceed inland in India they diminish ; at the Himalayas they cease. Two Indian 

 species l only have been observed to exist in Afghanistan ; and they are amongst the most 

 widely distributed of their respective genera. Neither of these extends in the north-east, either 

 to Western Turkestan or Yarkand. In Western Turkestan, it is true, three genera of this 

 order are represented ; but they have evidently extended southwards. Yarkand and Tibet 

 appear to be unsuited for this order of fishes : and thence none have been brought. 



The Physostomi include all the Yarkand and Tibet fishes. Among Siluroids the Indian 

 genera Callichrous and ? Amblyceps have been doubtfully recorded from Afghanistan ; but 

 neither have spread to Western Turkestan, where, however, the Silurus glanis is found, evi- 

 dently a wanderer from its more northern home. 



It is clear that in India there is a gradual diminution of Siluroids as we proceed inland 

 until we arrive at the Himalayas. On the slopes of these mountains we at first obtain a few 

 peculiar genera and species organized for a mountain-torrent life ; but as we rise, eventually 

 (as was the case in this Mission), an elevation is attained which, taken in connection with the 

 latitude and paucity of food, seems to be beyond the limit of the Indian Siluroids. 



The Siluroids along the slopes of the Himalayas appear to be mostly confined to the 

 following : A few, as Macrones and Callichrous, ascend a short distance, which may be con- 

 sidered accidental. Pseudecheneis is a more distinct hill-form, possessing a sucker formed of 

 transverse folds between its pectorals on the chest, and by the aid -of which it prevents itself 

 being carried away by the torrents. Glyptosternum has also an adhesive sucker, but of longitu- 

 dinal folds, and likewise placed on the chest. These fishes, however, appear to be more 

 intended for rapid rivers in the plains, but some ascend the slopes of the Himalayas. I have 

 taken large specimens from the rivers at the base ,of the hills in which the suckers were 

 scarcely visible : whether they had outgrown them, or, owing to the suckers not having been 

 primarily well developed, they had been unable to maintain their footing in the hill-streams, 

 of course, one cannot decide. Amblyceps is a Loach-like form found in the waters of the 

 plains and also of the hills ; it is abundant near Kangra. Exostoma, an example of which 

 exists in the Yarkand-Mission collection, is also a remarkable form. It has a broad and 

 depressed head and chest, the latter forming a species of sucker to enable it to sustain a 

 mountain-torrent life. 



This fish (Exostoma stoliczkce) belongs to a genus which has only been recorded from 

 hilly regions, neither extending to the waters of the comparatively level plateaus of the high 

 lands, nor descending any distance towards the plains. The following six species are known : 

 (1) E. stoliczkce, from the head-waters of the Indus ; (2) E. blythii, from near Darjeeling, 

 where the waters descend to the Ganges ; (3) E. labiatum, from the Mishmi Mountains and 

 Eastern Assam ; (4) E. andersonii, from near Bhamo on the confines of China; (5) E. 



1 Ophiocephalus gachua and Mastacembi-lus armatus. 



