ceivc Neritina fluviatilis (adhering to stones covered, 

 with water), although last year, and again in a few sub- 

 sequent days, they were abundant. During the present 

 January Limneus pereger and Planorbis cornea were 

 several days noticed moving about, and in February 

 Helix hispida, Helix lucida, and Vitrioa pellucida. 



Certain water shells, such as pass their lives in 

 ditches, can remain alive for a length of time when 

 their respective localities have been dried up by con- 

 tinued fine weather; at these periods Planorbis vortex 

 seals the aperture of its shell with a white calcareous 

 cement. In some experiments I found that the large 

 coil shell (Planorbis cornea) could be kept a month ou t 

 of water, and survive on again being placed in their, 

 native element. A land shell (Helix hispida) also was 

 retained underwater for a fortnight, and four specimens 

 our of five remained alive. Some shellfish brought 

 from Valparaiso, which were packed in cotton for up- 

 wards of a year, revived again. Snails, shut in a box 

 with air, close themselves in their shells, and will lie 

 dormant for many months. 



Shells are in various ways used as an article of com- 

 merce. They are manufactured into many beautiful 

 commodities, are used by painters for containing dif- 

 ferent colours, the sea cockle is the circulating medium * 

 of Angola; in jewellery, we are indebted to the Pearl 

 oyster, and less frequently to the English Unio Marga- 

 ritiferus for beautiful pearls ; and many are used to 

 supply the necessaries of life, amongst these are the 

 oyster, mussel, cockle, perriwinkle, Pecten maxim us, 

 &c. Amongst European fresh-water sheJls, although 

 none are eaten in England, yet in the south of Europe 

 the Unio tribe are devoured with avidity, either roasted 

 and drenched with oil, or scattered over with bread 

 crumbs and scalloped. Amongst the land shells Helix 

 b2 



