560 REPORT—1850. 
Dentalium tarentinum. 
Emarginula rosea. 
Adeorbis subcarinatus. 
Calyptrzea sinensis. 
Sealaria clathratulus. 
Nassa varicosa. 
Chemnitzia scalaris. 
Modiola barbata. 
Area lactea. 
Cytherea chione. 
Cardium aculeatum. 
Diplodonta rotundata. 
Venus verrucosa. 
Gastrochena modiolina. 
3. The following species increase in frequency of occurrence as we proceed 
from north to south :— 
Chiton fascicularis. 
Trochus granulatus. 
Rissoa crenulata. 
Sealaria clathrus. 
Cerithium adversum. 
Cerithiopsis tubercularis. 
Clavatula rufa. 
Modiola tulipa. 
Mactra subtruncata. 
Pecten varius. 
4. On the other hand, a greater number of species become more frequent 
in proceeding from south to north, showing thereby the more powerful in- 
fluence of the Scandinavian element in our fauna :— 
Dentalium entalis. 
Chiton cancellatus. 
Emarginula Mulleri. 
Trochus millegranus. 
Lacuna crassior. 
Chemnitzia fulvocincta. 
Eulimella MacAndrei. 
Natica Montagui. 
Fusus gracilis. 
Trophon Bamfium. 
Bela turricula. 
Tapes pullastra. 
Cyprina islandica. 
Astarte danmoniensis. 
Astarte compressa. 
Lucina borealis. 
Lucina flexuosa. 
Modiola vulgaris. 
Leda caudata. 
Lima subauriculata. 
Pecten tigrinus. 
5. The power of the Scandinavian element is still more strongly shown in 
the number and character of species, which are peculiarly northern: — 
Chiton Hanleyi. 
Acmea testudinalis. 
Propilidium ancyloide. 
Scissurella crispata. 
Chemnitzia rufescens. 
Natica greenlandica. 
Velutina plicatilis. 
Trichotropis borealis. 
Trophon Barvicense. 
Bela decussata. 
Mangelia brachystoma. 
Mangelia Boothii. 
Bulla hyalina. 
Bulla Cranchii. 
Bulla akera ?. 
Bulla quadrata. 
Bullza scabra. 
Pecten danicus. 
Pecten striatus ?. 
Crenella decussata. 
Crenella nigra. 
Pecten niveus. 
Astarte elliptica. 
Astarte crebricostata. 
Lucina ferruginosa. 
Poromya anatinoides. 
Nera costellata. 
Neeera abbreviata. 
To which may be added certain species found in the southern part of the 
British seas only in a few isolated patches, spaces which I regard as “glacial 
outliers,” as— 
Pilidium fulvum. 
Emarginula crassa. 
Rissoa abyssicola. 
Scalaria Trevelyana. 
Terebratula Caput-serpentis. 
Crania norvegica. 
Arca raridentata. 
Nucula decussata. 
Nucula tenuis. 
Leda pygmea. 
Nera cuspidata. 
Syndosmya, intermedia. 
Cardium suecicum. 
=—e-” ~~ 
