1919-] N. Annandale : Bombay Streams Fauna. 121 



lives on the surface of water, and as a rule, though not invariably, 

 of still water, in the structure of its feet, more particularly of 

 those of the two hinder pairs of legs. On these feet there is in 

 Gerris a pair of slender, almost bristle-like claws, which are 

 situated at the tip of the limb; some distance in front of them, 

 on the lower surface, there is a large bristle, but there is no 

 definite empodium and the whole structure is degenerate. In 

 Onychotrechus the claws are real claws, of a horny consistency, 

 curved, towards the tips, sharply pointed and flattened from side 

 to side ; they are separated from the extremity of the limb Vjy 

 several strong bristles and small processes perhaps of a sensory 

 nature; similar processes also occur just behind the claws, and 

 between them protrudes a coiled band-like empodium. These 

 structures deserve a more detailed examination, I refer to them 

 here merelj'' to indicate that the foot is modified in this genus to 

 enable it to cling to slippery surfaces, while in Gerris,^ which 

 apparently does not use the claws of its hinder legs at all, they 

 are degenerate. There is less difference between the anterior feet 

 of the two genera, both of which probably use them for grasping 

 prey, but even in these feet the claws of Onychotrechus are much 

 stronger and larger than those of Gerris. These facts are illus- 

 trated in figures 8 and 9 on plate III, drawn on the same scale 

 from insects of approximately the same size. 



Oligochaeta. — Small white worms of the family Naiadae are 

 abundant in damp algae on the cliffs. 



The fauna of these cliffs, where they are wet with the spray 

 of waterfalls, includes, therefore, highly modified forms among 

 both the MoUusca and the insects. The latter are still imperfectly 

 known, but there is every reason to think that a proper entomo- 

 logical investigation of the waterfalls would have great biological 

 interest. 



IV. Some Frogs from Streams in the Bombay Presidency. 



Only three species of frogs were found at the edge of the 

 streams investigated at Medha and Khandalla. They are Rana 

 cyanophlyctis, an undescribed race of R. Umnocharis for which I 

 propose the subspecific name syhadrensis, and an undescribed 

 species of Ixalus, which I have called /. hombayensis. Both new 

 race and new species are abundant in the Bombay Ghats. The 

 Ixalus has been found in the North Canara, Satara and Poona 

 districts, the race of R. Umnocharis in the two latter and also in 

 the Nasik district; neither form is known to occur at altitudes 

 below 2,000 or above 4,000 feet. 



^ I have seen a species of Gerris clinging to rocks at the edge of the Bhavani 

 river by means of its anterior claws. It could not, however, run about on the 

 sHppery surface. 



