LAND AND FRESH-WATER SHELLS. 351 



boues almost straight or the least exciirved for some distance, then 

 at an obtuse angle becoming oblique before rounding into the ex- 

 tremity, which is a little more sharply curved than the anterior end. 

 Ventral outline either faintly excurved, straight, or the least concave. 

 Interior bluish-white, most iridescent at the hinder extremity, 

 generally stained in parts with olive-brown. Cardinal tooth of the 

 right valve moderately large, four or five-lobed at the top, situated 

 juj>t in front of umbo. Between it and the outer margin is a short 

 ridge, the space between the tooth and the ridge I'eceiving the single, 

 smaller, roughened, and striated tooth of the left valve. Lateral 

 tooth of the right valve long, obliquely truncate behind, fitting in 

 between two teeth in the opposite valve. Anterior adductor scar 

 deep, posterior superficial, squarish in front. Pedal scar in both 

 valves under the cardinal tooth very deep. Ligament elongate, 

 prominent. 



Length 80 ram. ; height 38 ; diameter 21. 

 „ 70 mm. ; „ 35 ; „ 18. 

 This species recalls to mind some of the forms from Australia and 

 New Zealand. Its principal features are the elongcxte compressed 

 form, dark brown colour, wrinkled apices, and coarse incremental 

 lines. It is the only species as yet recorded from the Solomon 

 Islands. 



ADDITIONAL NOTE. (H. B. GUPPY.) 



A species of the Litoritinidce {Littorina scabra) is commonly found in 

 this group on the leaves and trunks of mangroves, Barringtonias, and other 

 littoral trees, the branches of which overspread the rising tide. These 

 molluscs occur at heights varying from one or two fett to eight or nine 

 feet above the high-water level ; and they possess an unusually delicate 

 opei'culum as compared with those of other species of the same family. 

 They do not seem to be able to withstand immersion in salt water for any 

 length of time, since out of six individuals kept submerged for tv/entv-four 

 hours, three died. When first placed in the water, they were evidently 

 very much out of their element, and tried in vain to creep out of the vessel. 

 The delicate character of the operculum indicates a transitional stage be- 

 tween marine and terrestrial molluscs ; and the experiment above referred 

 to, throws a little light on this subject, since only the yount^er of the six 

 individuals survived. One would have expected that the younger individ- 

 uals would have been less able to withstand immersion in sea-water, but 

 such was not the case, since they recovered from an immersion which killed 

 the older individuals. In explanation of this nm-xpected result, I would 

 infer that, on the theory of the inheritance of peculiarities at corresponding 

 nges, the younger individuals would retain more of the marine habits of the 

 oiULiinal parent of tlie spi-cies, because in the first place only tlie a'lults of 

 this parent species would have been modified to suit the new condition. 



