iQii.] ^. B^St-ewart : Cyprinidae from Tibet. 83 



The differences between the specimens from the Pamir and 

 those from the Nyang-chu at Kang-ma may be due to differences in 

 the character of the waters they inhabit or to differences in 

 nutrition. The Nyang-chu is a stream of a most muddy character 

 and it is possible that muddiness of the water, by interfering with 

 respiration, tends to cause an increase of the gill-surface and 

 hence an increase in size of the gill-containing portion of the head. 



It should be noted that the relative breadth of the head is 

 less in group G. 2 than in group G. i although these two groups 

 are composed of young fish of practically the same size. G. i 

 were obtained m the muddy streams around Gyantse, G. 2 from 

 marsh pools close to Gyantse the water of which was entirely free 

 from mud. The value of this observation is of course considerably 

 diminished by the small numbers of the fish in the two groups 

 and their small size. 



The specimens from the Nyang-chu were also exceptionally 

 fat and well nourished, whereas those from the Pamirs were of a 

 more hungry appearance. 



6. There are considerable variations in the colour of different 

 individuals. The Chumbi race is roughly separated in this respect 

 from the Nyang-chu race. 



The following is a note of the colour of a fresh fully grown 

 fish from the Nyang-chu: "Head and body above the latera 

 line a mixture of olive-green and slate-blue, this colour extending 

 somewhat below the lateral line posteriorly. A faint purplish 

 stripe about 3 mm. broad along each side of the dorsal line, com- 

 mencing at the dorsal fin and extending backward. Flanks below 

 the lateral line rather dull orange-gold; belly dull white." 



In the Chumbi valley, on the other hand, the back is pale 

 olive in the anterior half, pale steel-blue in the posterior, and the 

 black pigment is concentrated into irregular spots which are not 

 by any means closely set. The ground colour of the head in spirit 

 is greyish white. The flanks have the golden tinge, but the belly 

 is silvery. Altogether the Chumbi fish is more elegant than its 

 heavily-built cousin from the north, Steindachner (7) describes 

 the colour of the Leh specimens as follows: " Die obere Korper 

 halfte ist grau, die untere silberfarben. Kopf, Rumpf und Flossen 

 sind mit kleinen schwarzbraunen Flecken und Piinktchen gesch- 

 prenkelt," — apparently they resemble the Chumbi specimens. 



Specimens from Phari, Guru and Dochen are intermediate 

 between those of Chumbi and the N3'-ang-chu in respect of colour 

 as well as of general shape. They have the spots of the former 

 but less clearly defined, and the olive ground colour of the back is 

 lighter than in the Nyang-chu and darker than in the Chumbi race. 



As I have stated above, the Ssewerzoff type is more often 

 spotted than the Stoliczka : thus Ch. and P. 4 are mainly spotted 

 whereas K. i are entirely plain. On the other hand several in D. 

 I are spotted. 



In the fry (70 mm, and under) the back is of a chocolate-brown 

 with a slight tinge of slate, and there are two rows of irregular 



