8 Proceedings. 



Evening Meeting. — Febeuaey 15th, 1884. 

 Mr. Henry Tuke Mennell, F.L.S., of Croydon, exhibited 

 a large collection of Land and Fresli-water Shells, and read 

 a paper, entitled 'A Plea for Collecting Shells.' 



The relations of this study with Geology are very intimate. 

 All the great families of MoUusca existed as now in earliest 

 geological times, though recent species of shells are found 

 fossil only in the most recent strata. In the Coralline Crag, 

 out of 340 fossil species, 73 are now living as British and 

 some others are now living in more southern seas. The 

 Common Whelk abounds in recent geological strata, but it is 

 a curious fact that the fossil whelks are turned the opposite 

 way from the recent shells. The prevalence of certain families 

 and groups at various geological periods varies greatly, yet all 

 the great groups are present in the earliest organic rocks. 

 This is a most important and interesting fact in its relation 

 to development. 



Cephalopoda, including Cuttles, Nautilus, Ammonites, &c. 

 — 190 species are now living, against 1500 fossil species. 



PuLMONiFERA. Land Snails, &c. — 4300 species are now 

 living, against 460 fossil species. But we must bear in mind 

 that the fossil marine record is far more perfect than the 

 fossil land record. 



Bkachiopoda. Bivalves with unequal parts. — 75 living 

 species, against 1300 fossil, of which half were British. 



Conchifeka. Bivalves. — 3100 living species, against 5600 

 fossil. 



It is remarkable that the Cephalopods, though the highest 

 group, are yet the most abundant fossils. Development is 

 more evident in the succession of families withm the great 

 groups than in the groups themselves ; e.g., in Cephalopoda, 

 the lower-organised families, the Belemnites attain their 

 highest development and grow scarce just as the higher 

 Cuttlefishes appear on the world's stage. Many whole 

 families or groups have been lost. Against 100 fossil species 

 of Nautilus, but 4 are recent ; against 500 to 600 fossil species 

 of Ammonites, none remain. 



The Bkachiopoda were most widely distributed in geological 



