1922.] S. L. Hora : Fish of Mountain Torrents. 33 



The figures illustrating this paper were drawn by me with the 

 help of a camera lucida. 



The types selected for the study of hill-stream adaptations 

 belong to the two chief orders of Indian freshwater fishes, the 

 Cyprinoidea and the Siluroidea The genera on which observations 

 have been made are the following : — 



Cyprinoidea. Siluroidea. 



Balitora Gray. Ercthisles Mull. & Trosch. 



Phavania Hora. Glyptosternum ' McClelland. 



Psilorhynchus McClelland. Pseudecheneis Blyth. 



Parapsilorhynchus Hora. Glyptothorax ' Blyth. 



Garra Ham. Buch. Laguvia" 1 Hora. 



All these genera are found only in small mountain torrents, 

 with the exception of certain species of the genus Garra which 

 descend into streams of fair size. All show special adaptations to 

 this environment. 



The Schizothoracinae and some of the species of Nemachilus 

 which live in rapid-running rivers show similar but less well- 

 marked adaptations. Some remarks on the nature of the adhesive 

 apparatus of these forms are also included in this paper. 



1 While recently attempting to revise the species of the genus Exostoma 

 Blyth, I have found that this generic name canot be employed for the forms to 

 which it is usually assigned. I propose the following changes in view of the 

 facts given below : — 



Exostoma Blyth = Glyptosternum McClelland. 

 Glyptosternum McClelland ^Glyptothorax Blyth. 

 McClelland (Calcutta Journ, Nat. Hist. II, pp. 584-585, and 587-588,1842) 

 described five species, Glyptosternon reticulatus, G. sulcatus, G. striatus, G. 

 pectinopterus and G. labiatus under the new generic designation Glyptosternon. 

 Blyth (Journ. As. Soc. Bengal XXIX, pp. 153-155. i860) split up these five 

 forms into four distinct genera, Glyptosternon, Pse:ideclieneis, Glyptothorax and 

 Exostoma. He regarded G. reticulatus from Alghanistan as the type-species of 

 McClelland's Glyptosternon. According to McClelland this species is stated tn 

 be " without spines ; the first ray of the pectoral and ventral fins soft and pinnate, 

 giving off soft pointed cartilaginous rays along the anterior margin ; which are 

 enveloped in the membrane of the fin. The nude surface and anterior portion 

 of the body form a flat corrugated surface." Of the several species of Exostoma 

 in the collection of the Indian Museum, all except E. berdmorei, possess the outer 

 ray of the pectoral and the ventral fins similar to that of McClelland's Glyptosternon 

 reticulatus ; they ought, therefore, to be included in the same genus. Exostoma 

 berdmorei, Blyth, which is known from a single specimen from Tenasserim, now 

 in a very bad condition, is the type-species of the genus Exostoma. The pectoral 

 spine of this species is totally different from that of the others and corresponds to 

 those forms which were included by Blyth under his genus Glyptothorax. The 

 absence of a " pectoral disk," which led Blyth to separate the genus Exostoma 

 from Glyptothorax, is not a valid generic distinction, because the thoracic adhesive 

 apparatus of almost all the species included in the genus Glyptothorax may be- 

 come indistinct in specimens which are old or have been badly preserved. 



The generic name Glyptosternon, McClelland was latinised into Glyptoster- 

 num by Giinthcr (Cat. Fish. Brit. Mus. V, p. 185, 1864). 



2 In a paper published recently (Rec. Ind. Mus. XXII, p. 730, 1921) I have 

 given reasons for separating Erethistes asperus (McClelland) (Calcutta Journ. 

 Nat. Hist. IV, p. 404, pi. xxiv, fig. 2) along with the two new species from the 

 base of the Darjiling Himalayas from the genus Erethistes and have placed them 

 all in a new genus Laguvia. This genus is intermediate in certain respects 

 between Erethistes and Glyptothorax. 



