1898.] WBI.CH. — Land- Shell '^Pockets" 07i Sand- Dimes. 81 



Standen, in their paper {Journ. of Conch., 1896), on the shells 

 of Dog's Bay, mention that the thick, large, and very heavy 

 shells of Helix Jiemoralis in the lower zone, seem to point to 

 just such favourable conditions for moUuscan life. 



I made a rough analysis of this deposit, and found that 

 87 per cent, of it dissolved quickly in hydrochloric acid, the 

 small residue being composed of very nne quartz sand and 

 mica, which had probably blown up with the foraminifera 

 from the old strand. 



On our Northern strands, the proportion of fine foramini- 

 ferous, &c., material is very much smaller, and though some 

 of this finds its way to the dunes still forming, the mass of 

 the material composing them is mainly silicious. Any cal- 

 careous matter mixed with it seems to get quickly dissolved 

 by the percolation of rain-water through the sand ; this too, as 

 well as the drifting of the sand, probably accounts for the thin 

 eroded shells in the old laj^ers or '' pockets." Possibly the 

 partly solidified beds of sand present at the base of some 

 dunes, at Portstewart and especially Portsalon, are sandstones 

 now partly consolidating by the aid of carbonates formed at 

 the surface in this way, which are carried down in solution 

 and set free at the bottom, to bind the sand particles together. 



In proof of this, a sample of sand from the upper part of a 

 dune close to a strand, the surface of which was more 

 calcareous than usual, yielded only 2*5 per cent, of carbonate 

 of lime, the residue being silicious. 



To show the richness in shells of the material, both in 

 quantity and quality, I give the number of the smaller speci- 

 mens in three ounces, sifted out of about a pint collected 

 from, the large *' pocket" at Portstewart referred to. 



Vertigo a^igustior, 158 ; V. pygmcea, 92 ; V. substriata^ 47 ; 

 V. picsilla var. albina., 8 ; V. ede^ihda, i ; Helix acnleata, 34 ; 

 H. pygmcea, 24 ; H. pidchclla in profusion ; Hyalinia crys- 

 tallina, 18; H. fulva, 6; Carychium viinimuni, 28 (these out 

 of fifty grains of the finer material) ; and in varying numbers, 

 many of them being 3^oung shells, Hyali^iia alliaria, Hyalinia 

 (sp. ?), Helix acuta, H hispida, H. nemoralis, Pnpa viuscorum 

 and var. albi7ia, H. cylindracea and var. albina, Clansilia 

 bidentafa, Cochlicopa lubrica, Hydrobia Jeyikinsi — twenty-one 

 species in all. 



