Sir H. H. Howortli — Geological History of the Baltic. 401 



Cardmm edule. Tellina (Macoma) BaWiica. 



Cardiuvi var. *Corbula gibba. 



Tapes pidlastra. *Modiolaria discors. 

 T. aureus. Montacuta bidentata. 



* T. ■ decussatus. Scrobicularia piperata . 



This list differs from that given by Petersen in excluding Anomia 

 squaimda and in retaining the name Scrohicularia piperata which he 

 called S. /plana. It is perfectly plain that it only represents a 

 portion of the moUusca which were contained in the Southern 

 Cattegat when the raised beaches were deposited. Here the beaches 

 are all at a very low level; they form, in fact, the concluding factors 

 of a series which occur at declining levels as we proceed southwards, 

 but were doubtless deposited synchronously at different points on the 

 coast from the Christiania Fjord to the Oresund, and represent only 

 the littoral series. It is, in fact, interesting to compare a small section 

 of the Gulf, namely, the Holbeck Fjord, where the following shells 

 are now living which have not occurred in the raised beds. 



Buccimwi undatum. Mactra subtruncata. 



Tectura testtidinalis. Thracia papyracea. 



Abra alba. Saxicava rugosa. 



A. nitida. My a truncata. 



Solen pellucida. M. arenaria. 



What is much more important and interesting is the absence from 

 the present waters of the Southern Cattegat of a number of shells 

 with a wide distribution which abound in the raised beaches and 

 also in the kitchen-middens of that channel. I have described at 

 some length the remarkable consequences which have been deduced 

 from this absence in previous papers (Geol. Mag., 1905, pp. 12-15, 

 557-9). The general conclusion of the arguments of Petersen and 

 others is that the extermination or emigration of these molluscs "was 

 due to the Baltic breach which flooded the Cattegat with an excess 

 of fresh water, and that this was coincident with the end of the 

 kitchen-midden people. It enables us to roughly date that event at 

 some eight or nine thousand years ago. The only fresh fact I need 

 mention is the addition of Pholas candidus to the list of migrants. 

 It is not now found nearer than the south of Norway. 



By far the most interesting of these absentees are the oyster and 

 the three species of Tapes. Petersen named the beds in which he 

 found this series of sliells Tapes beds, and he proceeded to argue that 

 when they Avere deposited the waters of the Southern Cattegat were 

 not only salter but probably also warmer than they are now, and 

 approximated more to those of the Skagerack than the North Sea. 



In regard to tlie connexion of the Baltic with the Cattegat, it is 

 interesting that while the oyster has never occurred in the Litorina 

 deposits in the Sound, it has occurred in the deposits of the Great 

 Belt probably as far south as the Svendborg district {Aarh.for Nord. 

 Oldlc. Hist., p. 321, Copenhagen, 1888), sliowing that before the 

 Baltic breach the Belt was open from the north as far at least as the 

 latter place. 



Morlot's observations made long ago prove that the "kitchen- 

 middens" in many cases show signs of stratification and of having 



DECADE VI. — VOL. V.— NO. IX. 2& 



