82 



Records of the Indian Museum. [Vol. XXIV, 



I have noticed similar modifications in mature males of several 

 other Indian species of the genus. In the Central Asiatic forms, 

 however, the secondary characters of the male are more marked 

 and somewhat complicated. Of the thirteen species of the genus 

 Nemachilus referred to in this paper, seven show marked sexual 

 dimorphism. The male in these is usually provided with a raised 

 tuberculate area below the nare.s, separated ventrally by a groove 

 from the adjacent parts of the skin. The area is almost rectan- 

 gular, commencing at the corner of the lips and extending poste- 

 riorly below the anterior third of the orbit. In certain species such 

 as N. tenuis, N. yasinensis and N . tibetanus (fig. 4), there is another 

 tuberculate area immediately behind the first one. Sometimes 

 the tubercles are irregularly scattered on the operculum and the 

 sides of the head behind the eyes. In all species that exhibit 



Text-fig. 5. — Tubercles covering secondary sexual pads of male of N. 

 tibetanus (highly magnified). 



sexual dimorphism, the pectoral fin-rays are provided with 

 thickened tuberculate pads on their dorsal aspect. These 

 tubercles on the fin-rays are not to be confused with encysted 

 glochidia, which are sometimes found in this position, though they 

 resemble them closely. A few scattered tubercles are sometimes 

 found on the under surface of the pectoral fin-rays. 



In both the species of the genus Diplophysa in our collection, 

 the male is modified on exactly the same lines as has already 

 been described for the genus Nemachilus. 



The structure of the tuberculate areas is somewhat interesting. 

 Each of the tubercles is provided with a short, stout spine-like 

 outgrowth (fig. 5) which is sharp and slightly curved towards the 

 end. The spine rests on a broad cushion-like rounded base. 



Recently I have collected an interesting specimen of 'Nema- 

 chilus from the Simla Hills. It possesses a groove and a small 



