136 REPORT — 1839. 



the latter coralline oolite and chalk. We must attribute the 

 richness of this district in species to the predominance of the 

 positive geological influence. In the neighbourhood of Sun- 

 derland, in the magnesian limestone, sixty-four species occur. 

 Of these the following are considered peculiar to the limestone 

 in that locality : Helix glabella, pulchella, rupestris, and 

 variabilis, Clausilia dubia, Balea fragilis, Pupa pygmcEa, 

 and Acme lineata. Judging from Mr. Bean's list, the calca- 

 reous strata of the neighbourhood of Scarborough must be 

 especially favourable to the variation of species. Thus he 

 mentions 152 varieties of Helix hortensis, fifty-eight of his 

 Helix pullata (a white-mouthed form o^ Helix hortensis), 226 

 of Helix nemoralis, and twenty-one of its variety, Helix nota- 

 bilis. Among the rarities of the north-eastern district. Pupa 

 alpestris, Pupa anglica, Helix scarburgensis and excavata, 

 and Planorbis IcEvis are conspicuous. In this district we find 

 the northernmost British localities for Helix carthusiana and 

 lapicida. Acme lineata, Clausilia laminata, dubia, and ventri- 

 cosa, Planorbis corneus, and Limn eus glutinosus ; also for Ci/- 

 clostoma elegans among the terrestrial Pectinibranchia. Dr. 

 Greville has communicated the remarkable fact, that the Helix 

 aspersa, so universal in England, is absent from the neigh- 

 bourhood of Craven in this province. 



In certain localities, MoUusca, generally distributed in most 

 places without reference to geological structure, are confined 

 to particular strata. This is remarkably shown in the follow- 

 ing list of species observed by Mr. Bean to be peculiar to the 

 calcareous strata in the neighbourhood of Scarborough : Helix 

 ericetorum, variabilis, umbilicata, caper ata, radiata, pulchella, 

 and lapicida ; Bulimus obscurus. Achat ina acicula, Azeca 

 Matoni, Clausilia laminata and rugosa, Balea fragilis, Pupa 

 umbilicata, marginata, and pusilla ; Helix carthusiana and 

 Helix umbilicata confined to the chalk. In the neighbourhood 

 of Bamborough Helix caperata, and H. variabilis are found 

 together on trap, an unusual locahty for the latter species. 



District V. — The fifth or north-western division of England 

 is similar in character to the fourth, though not so rich in spe- 

 cies, those of the chalk and oolite being absent. The rarer 

 species, found in the carboniferous strata of the last district, 

 are found also in similar localities in this. The new red sand- 

 stone, constituting a large portion of this division, exercises no 

 perceptible influence in favour of the increase of species. The 

 presence of Bulimus acutus indicates the western climatal in- 

 fluence. Planorbis corneus is absent from the waters, and 

 Limneus stagnalis appears for the last time on the western 



