12 SECOND YARKAND MISSION. 



Habitat. From Sind throughout India and Ceylon, and generally ascending mountain 

 rivers for the purpose of breeding. Should such rivers be snow-fed, it deposits its ova in the 

 side streams. 



Before describing the Loaches, I will give my reasons why it appears to me that the 

 genus Diplophysa, Kessler, may probably be a synonym of Nemacheilm. 



It is said to consist of " elongated fishes, strongly compressed posteriorly," which we 

 perceive in Nemacheilus stoliczkts and N. yarkandensis ; but in an equally elongated species 

 N. tenuis, the free portion of the tail is not compressed, but is as wide as deep. 



" The eyes are surrounded with a fold of skin forming a lid." This is also perceived in 

 specimens amongst the species I have enumerated from Yarkand ; and I have likewise noted 

 that some of the other fishes from the same cold region have folds of skin more or less cover- 

 ing the eyes. 



" Lips fleshy, the upper more or less denticulated, the inferior bilobed, and more or less 

 papillated." I have figured the inferior surface of the head of all the Loaches ; and 

 although some, as N. stoliczkce and N. tenuis, have the lips as described by Kessler, the 

 N. yarkandensis has not, whilst the three certainly cannot be separated into distinct genera. 



" Air-vessel in two parts, the anterior enclosed in a bony capsule, the posterior elongated 

 and free in the abdominal cavity." This is the only portion of Kessler 's definition not perceived 

 in these fishes in which the air-vessel is enclosed in bone ; and I cannot resist suggest- 

 ing a re-examination of "Western Turkestan specimens. It would be very remarkable were 

 the Nemacheili found in Europe, in fact throughout Asia, even in the Oxus, to have their 

 air-vessels enclosed in bone, whereas in the river Hi going to Lake Balkash, and the river 

 Urdjar falling into Lake Ala (Ala-kul), they have the same organ partially free in the 

 abdomen, as is seen in genus Sofia. But granting Kessler's description to be accurate, I 

 cannot think that such a fact alone would justify instituting a new genus for the reception of 



his species. 



The reason for air-vessels being more or less enclosed in bone in some fishes is obscure ; 

 and I some time since adverted, in the ' Proceedings of the Zoological Society,' to the circum- 

 stance of such not being infrequent in Indian Siluridce. 



I found amongst the Indian genera of Siluroids of the fresh waters, or those which entered 

 fresh waters, as follows : 



^4. Air-vessel, when present, free in the abdominal cavity 



1. Rita; 2. Erethistes ; 3. Pseudeutropius ; 4. Silurus ; 5. Olyra ; 6. Macrones ; 7. 

 Callichrous ; 8. Wallago ; 9. Arius ; 10. Hemipimelodus ;' 11. Osteogeniosus ; 

 12. Batrachoceplialus ; 13. Pangasius ; 14. Plotosus. Of these, five (Nos. 

 9, 10, 11, 12, and 14) are marine forms, entering fresh waters for predaceous 

 purposes. 



B. Air vessel more or less enclosed in bone 



1. Ailia ; 2. Ailiichthys ; 3. Sisor ; 4. Bagarius ; 5. Amblyceps ; 6. Saccobranchus ; 

 7. Silundia; 8. Eutropiichthys ; 9. Gagata ; 10. Nangra ; 11. Pseudecheneis ; 

 12. Exostoma ; 13. Clarias ; 14. Qlyptosternum. All of these are fresh water 



genera. 



Hemipimelodus appears to be Arius destitute of teeth on the palate. 



