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



In Balilora they are short and stumpy and liable to be overlooked. 

 In the remaining hill-stream genera discussed in this paper they 

 are short and thread-like. In Parapsilorhynchus, however, they 

 are short and cylindrical. 



In Nemachilus and the Homalopterid genera the lips are so 

 modified as to form a sucker with the help of the mouth, and 

 consequently they exhibit diverse modifications and specializations. 

 In the genus Nemachilus the lips are divided in the middle and are 

 greatly swollen, so that when they are pulled outwards away from 

 the mouth, their divided parts form a continuous ring-like sucker. 

 In most cases the skin of the swollen region is plicated, but I have 

 not been able to find any trace of definite spines such as will be 

 described later in the structure of the adhesive apparatus of other 

 genera. I have already described in a previous paper l the way 

 in which, by the action of certain muscles, the lips of Bhavania 

 annandalei are converted into a sucker. In Balitora the thick lips 

 are cut up into several tentaculate processes and when pulled apart 

 they form an effective sucker. In most of the species of the genus 

 Glyptosternum the lips are " reflected and spread continuously 

 round the mouth, so as to form a broad flat sucker." Similar 

 modifications occur in certain of the most specialized forms of the 

 genus Glyptothorax. 



6. The eyes. — With the flattening of the form in hill-stream 

 fishes the eyes are more and more pushed towards the upper 

 surface. In forms like Balitora brucei, B. maculata , Glyfalotharax 

 saisiij G. striatus., Pseudecheneis sulcatus and in almost all species 

 of the genus Glyptosternum the eyes are situated on the dorsal 

 surface and are placed close together. Besides this change in 

 position, they are much reduced in size. To what cause this re- 

 duction is due, I do not know; but it is quite probable that the 

 intensity of the light in the clear shallow waters of the hill-streams 

 may have something to do with it. 



7. The gill-openings , branchiostegal rays and membranes. — 

 With the employment of the under surface for the purpose of adhe- 

 sion to rocks and stones, the gill-openings are generally restricted to 

 the sides. Except in the genera Glyptothorax and Laguvia, the 

 gill-openings, in almost all the genera dealt with in this paper, 

 do not extend beyond the base of the pectoral fin on the under sur- 

 face. In certain species of Garra the openings are somewhat wider, 

 but even in them they are separated from each other by a con- 

 siderable distance. The greatest modification as regards this 

 character has taken place in two species of Glyptosternum. In 

 these the gill-openings are situated above the base of the pectoral 

 fin and there is a short narrow passage from the interior of the 

 gill-chamber to the exterior. 



With the restriction of the gill-openings to the sides, it is 

 natural to suppose that respiration will suffer to some extent. 

 Moreover, when a fish is feeding on the algal slime, the under 



1 Hora, Rec. hid, Mas. XIX, p, 203, pi. x, fig. 2. 



