LECTURE XII. 335 



effect is attributed^ does not seem to us a satisfactory explana- 

 tion. The Romans succeeded in transplanting oysters into tlie 

 freshwater lakes near Naples^ where they still live and propa- 

 gate^ and even mussels and periwinkles thrive well in brackish 

 water as well as in lakes periodically filled with fresh water. 

 The cause of the phenomenon must therefore be sought else- 

 where : in that slow transformation and alteration of the sea- 

 bottom, which has been found in oyster beds, and which is 

 chiefly produced by tubicoloe, which overgrow the oyster beds 

 and destroy them. 



Besides the shells mentioned above, there are found others 

 of species still living in the Danish waters, though in smaller 

 quantities, such as Buccimim retictdatuin and undatum ; Venus 

 ptdlastra, which do not seem to have been much relished by 

 these old mussel-eaters. 



But few remains of the crab are found, but many of the 

 herring, cod, lemon sole fPleuronedes UmandaJ, the eel, the 

 latter being chiefly found where it abounds at present. Of birds, 

 besides several species of wild ducks and geese, are found the 

 remains of the wild swan, woodcock, and the great auk fAlca 

 impennisj, which died out (Iceland its last refuge) in 1842. 

 The capercailzie (Tetrao urogallusj is no longer seen in Den- 

 mark, as the firs, on the sprouts of which it fed in the Spring, 

 have now mostly disappeared, whilst formerly they were very 

 abundant, as shown by the exploration of the peat bogs. The 

 swan comes to Denmark in the Winter only, proceeding in 

 Summer further north to Iceland ; but as even the auk, which 

 took refuge there, was formerly in all the Northern Seas, in 

 Denmark, the Faroe Islands, and the Hebrides, very abundant, 

 there is nothing against the assumption that the swan formerly 

 passed his summers in Denmark. Small land birds were not 

 found, the common fowl was entirely absent. 



Of quadrupeds, the bones found belonged to the stag, the 

 roe, the wild hog, the beaver, the seal, and the now extinct 

 'urochs' (Bos primigeniusj , which seems, among our present 

 races, to have left as his progeny the heavy Friesland cow. Of 

 the LithuanianBison, or Auerochs fBos ur'us, or BisonBnropoeus) 

 which is a distinct species, and formerly spread over all Europe, 



