1922.] 



S. L. Hora : Fish of Mountain Torrents. 



37 



sion. As regards the shape of the fins, some of the inner rays 

 are directed upwards against the sides of the body, so that when 

 the outer rays are used for the purpose of adhesion, the inner 

 rays can be kept constantly in motion, probably for the purpose of 

 respiration. I have embodied my observations on this point in an 

 immature specimen of Psilorhynchus in a former paper. 1 In the 

 genus Glyptostemum (fig. 8) only a few rays of the paired fins are 

 visible from the under surface, while the remainder are reflected up- 

 wards. I have not observed these fishes in nature, but on a recent 

 tour to the base of the Darjiling Himalayas, I was able to verify 

 the observation that I had previously made on the immature speci- 

 mens of Psilorhynchus from the Naga Hills, by keeping a half- 

 grown specimen of Garra annandalei in an artificial pond of water 

 in the course of the Mahanadi River. In Parahomaloptera micro- 

 stoma l the shape of the fins is somewhat less modified than is the 

 case in Glyptostemum. 



The greatest specialization as regards fin-structure is found in 

 Gaslromvzon bomeensis. The pectorals begin with a long base, 

 vertically below the eyes : the ventrals possess long curved bases, 

 which are united posteriorly. Between the bases of the ventral 

 and the pectoral fins there is a lateral extension of the abdominal 

 skin. " By this arrangement the whole flattened abdominal surface, 

 together with the fins and the flattened lower surface of the head 

 forms an enormous suctorial disc." 3 



I have already pointed out that the 

 outer rays or the spines, as the case 

 may be, of the paired fins are greatly 

 flattened. Interesting modifications 

 take place in the outer ray of these 1 

 fins in the genus Glyptostemum, " soft 

 pointci cartilaginous rays " are given 

 off along the anterior margin (fig. ia) 

 to support the striated skin which 

 forms the adhesive apparatus. This 

 is described in detail below when deal- 

 ing with the modification of the skin 

 in the formation of the adhesive appa- 

 ratus. 



The pectoral and the pelvic girdles 

 are modified in certain hill-stream 

 fishes, owing to the acquisition of new 

 functions by the paired fins. It is 

 unfortunate that I have not been able 

 to study these structures in Psilorhyn- 

 chus, Bhavania, Balitora and Homal- 

 optera, on account of the paucity of 



a/. 



T 



Pectoral spine 

 and Glypto- 



■:xt-fig I.— 



of Glyptotlwrax 

 sternum. 



a. Outer pectoral ray 

 Glyptostemum labiatum. 

 f>. Pectoral spine of Glypto 



thorax berdmorei . 



of 



1 Mora, Rec. hid. Mus. XIX, p. 212 (19201. 



1 Weber and Beaufort, Fislies Indo-Austr. Arch. Ill, p. 20. fig. 5 (1916). 



3 Weber and Beaufort, ibid., p. 2 (1910). 



