24 'Moll. 
MOLLUSCA. 
3. All those. which are more strongly developed or more numerous in 
the Arctic part of Norway than in its southern parts. 
4. All those which live near the surface in the Arctic part, and at a 
greater depth in the southern part. 
5. Those which exhibit several varieties in the Arctic region, and are 
more uniform in the southern part. 
6. Those which are more strongly developed in the large fjords than in 
the open sea. 
7. Those which occur in the cold area of the sea, beyond the littoral 
banks. 
8. All those which are observed in the Polar Sea of the northern coast of 
Siberia, Novaya Zemlya, Spitzbergen, Jan Mayen, or Greenland. 
9. Generally all those which are found also on the east coast of North 
America. 
10. The species which are found also in the Behring Sea. 
11. All those which are found in the older glacial beds in a fossil state. 
12. All which are' found more strongly developed in the fossil state than 
living at the same latitude. 
According to these rules, 275 out of the 401 species now living in the 
Arctic part of Norway are originally Arctic ; the rest, 126, are boreal ; 
pp. 392-404. Only those species will be mentioned infra which have not 
been figured or are not generally known. 
2 . Seas of Northern Europe. 
The Mollusca of the Firth of Clyde are treated by A. Browne, supra. 
Holland. List of Mollusca observed at the zoological station at the 
Helder, by D. van Haren-Noman ; Tijdschr. Ned. Dierk. iii. pp. 21-32. 
Note on the Mollusks of the littoral zone at Etretat, Dep. Seine-Inferi- 
eure, by P. Fischer, J. de Conch, xxvi. pp. 309-31Q. Sub- terrestrial 
region, first Alexia denticulata, lower Litorina rudis ; region of Balanus ; 
region of Patella vulgata^ above with Litorina litorea^ lower with L. 
ohtusata ; last region that of Purpura lapillus. 
Guernsey. A number of marine Mollusca, enumerated by A. H. 
Cooke & H. M. Gwatkin, Q. J. Conch. 1878, No. 15, pp. 324-332. 
Haliotis abundant, Buccinum undatmi rare, Litorina litorea did not occur 
to the authors. 
3 . Mediterranean Sea. 
T. A. DE Monterosato gives a new enumeration of the shells of the 
Mediterranean, amounting to 1021 species, viz., 302 Bivalves, 15 Denta- 
liidce, 685 Gastropods, 19 Pteropods, and 2 Cephalopods. He inclines 
much to keep the species of the Mediterranean distinct from those of the 
northern seas of Europe, in many cases in which they have been identi- 
fied by former authors ; for example, Mytilus galloprovincialis (Lam.) 
distinct from edulis (L.), Cardium lamarcki (Reeve) from edule (L.), &c. 
Giorn. Sc. Palerra. xiii. 55 pp. 
Note on the periodical appearance or frequcnco of some Mollusca in 
