40 



Records of the Indian Museum. [Vol. XXIV,' 



In the genus Glypto sternum , where the fins act as organs of 

 adhesion, the moidfications in the musculature are more marked 

 (fig. 4) and the arrangement is different. The muscle labelled 2 in 

 Glyptothorax correspond to 5 in Glyptosterimm ; muscle 4 is the 

 same in both cases. Muscle 1 arises close to the mid-ventral suture 

 of the clavicle and is inserted in the form of a glistening tendon 

 on the anterior border of the pectoral spine. Its action is to ex- 

 pand the fin. Muscle 2 arises near the mid-ventral line and is 

 inserted on the bases of the spine and the first few rays. Its func- 

 tion is, in all probability, to keep the spine and the few outer rays 

 closely pressed against the substance on which the fish ma}' be 

 testing. This muscle is large and is not found in any other genus 

 that I have studied ; it has no other muscles to counteract its 

 action. 



5. 1- 



Text-fig. 4. — Muscles of the pectoral fin in Glyptoslernum labiatum. 

 Numbers 1, 2, 3, 4 and 5 indicate the muscles referred to in the text. 



As regards the skeleton of the pectoral girdle in Glyplosteruum, 

 there are no bony ridges for the insertion of muscles. Otherwise 

 it is very similar to that of Glyptothorax. 



The pelvic fins also possess a special muscle (fig. 5) beside 

 the abductor and abductor systems. This keeps the fins closely 

 pressed against rocks, when the fish is resting, thus enabling it to 

 adhere to rocks by means of striated skin on the under surface of 

 some of the outer rays of the pelvic fin. 



4. The caudal fin and its peduncle. — There is a general ten- 

 dency amongst hill-stream fishes to possess a long, narrow, band- 

 shaped caudal peduncle. For example in Nemachilus tenuis and 

 N. lhasae the caudal peduncle is more narrow and elongated than 

 in any other species of the genus that I have seen. These 

 two species resemble the Central Asiatic forms figured by Herzen- 

 stein ' and it is possible that these features are correlated with high 



1 Herzenstein, YViss. Res. Przewalski Central- As Reis., Theil III (2), pis. 

 i-vii (if"' 



