400 Sir H. H. Howorth — Geological History of the Baltic. 



the jSTorth Sea by way of the Limfjord during one of the intervals 

 when it was open at both ends. Others may have been brought in 

 accidentally by ships or otherwise. 



So much for the absentees from the northern section. On the 

 other hand, the latter contains a considerable number of shells not in 

 the southern part. 



On comparing Petersen's lists of the shells from the two sections 

 of the Cattegat I find tlie following absentees from tlie southern 

 area : — 



Gasteropoda. 



1. Scalaria tortosa. 



2. S. Trevellyana. 



3. S. lactea. 



4. Volvzda acuviinata. 



5. Plviline pruinosa. 



6. Acera bullata. 



7. Lacuna pallidula. 



8. L. divaricata. 



9. L. membranacea. 



10. L. inconspicua. 



11. L. parva. 



12. NaticaMontagui. 



13. Capulus Hungaricus. 



14. Fusus propinquus. 



15. Mangelia costata. 



16. M. nebula. 



17. Trochus milligranus. 



18. Nacella pellucida. 



19. Dentalhmi (Antalis) entale. 



20. Chiton ruber. 



Lamellibeanchia. 



1. Pecten maximzis. 



2. Mytilus Adriaticiis. 



3. Modiolaria discors. 



4. Nuctda decussata. 



5. Gardium Norivegicum. 



6. G. nodosuin. 



7. G. edule. 



8. Lucinopsis undatum. 



9. Isocardia cor. 



10. Venus fasciata. 



11. Dosinia exoleta. 



12. Tellina pusilla. 



13. T. tenuis. 



14. Solen ensis. 



1-5. Mactra stultoruyn. 



16. Thracia convexa. 



17. Cochlodesma (Triforis'?) perversa. 



18. Lyonsia Norvegica. 



19. NecEra ciispidata. 



It is plain that while the southern section of the Cattegat ought 

 zoologically to be joined with the Sound, the northern part ought to 

 be united with the Skagerack and the Christiania Fjord. 



The reasons for the disparity in the contents of the two sections of 

 the Cattegat is probably the absence of the necessary quantity of salt 

 in the waters of the southern section. It may be also due partly to 

 the fact that the waters of the latter are not deep enough, the 

 greater part of it being in fact much shallower than the northern 

 part. Let us now return to the raised beaches of the Cattegat. In 

 them there is a marked contrast between their contents and the 

 living fauna of the great waterway. 



I will now give a list of the shells which have occurred in the 

 raised beaches and kitchen-middens. Those which are rare and only 

 occur occasionally are marked with an asterisk. 



Gasteeopoda. Cerithium reticulatum. 



*Odostomia sp. *Utricuhis truncatulus. 



*Trif oris perversa. ■ * Neritina fluviatilis . 



Litorina rudis. *Bissoa striata. 



L. obtusata. R- membranacea. 



L. litorea. Acera bullata. 



L. var. tenebrosa. 



Hydrobia sp. LAMELLIBEANCHIA. 



Lacuna inconspicua. Ostrcea edulis. 



*Z;. ddvaricata. Mytilus edulis. 



Nassa reticulata. Gardium exiguum. 



