LAND AND FRESH-WATER SHELLS. 343 



and independently of any alarm. The individuals of Neritina sub- 

 sulcata that I kept in a large bottle in my cabin, used frequently 

 in the course of a nisxht to detach themselves from the sides and 

 drop down into the water below. On one occasion when the noise 

 woke me up, I found the culprit voraciously eating a portion of de- 

 cayed leaf. In the daytime they sometimes dropped, and at other 



times crawled, down to the water It is probable that the 



musky water, which this Nerite ejects when it is picked off a rock, 

 ma}'' cause a bird to drop it from its beak and thus save its life. 



Amongst the new fresh-water shells that I found in this group 

 was a species of Unio, to which Mr. Smith did me the honour of 

 attaching my name, it being the first species of this genus of river- 

 mussels that has been found in the Solomon Group. But its occur- 

 rence there means something more than a new locality, since, as I 

 believe, I am correct in asserting, we have in it the first record of 

 this widely distributed genus having reached the Pacific islands. 

 I do not think that this species can be generally spread through the 

 Solomon Group. I only found it in one locality, namely the Short- 

 land Islands, near the western end of the group. 



A very familiar sliell, in low-lying moist and marshy situations 

 throughout the Solomon Islands, is that of the auriculoid, Pythia 

 scaraheus, Linne. Being usually accustomed to find it in the low- 

 lying districts, I was surprised on one occasion to find it in the 

 higher pai-ts of Faro Island, wliich attains an elevation of 1,900 feet 

 above sea. In the mangrove swamps and in the lower parts of the 

 streams at Choiseul Bay, I found a species of Cyrena which has not 

 yet been described, together with Cerithidea cornea (A. Adams: var.) 

 and Pyrazus palustris, the last species occurring also in India. On 

 the moist ground of the taro patches in the islands of Bougainville 

 Straits thrives a species (*S'. simplex, var.) of that ubiquitous genus 

 Succinea. The operculated land-snails, of which tlie Helicince are 

 the most numerous, are found more frequently in calcareous districtf. 



