EHRENBERG ON INFUSORIA IN MARINE MUD. 255 



the mud formation, deposited at the mouth of the Jahde, and the 

 other localities, contains innumerable multitudes of the same cal- 

 careous and siliceous -shelled animalcules as those existing in the 

 Elbe ; and further, that the Ems as far as the strong flood tide rises 

 (which, according to Dr. Pressel, extends to Halte and Weener), 

 is like the Elbe, extremely rich in calcareous and siliceous- shelled 

 microscopic marine animalcules, and that the rich slimy deposit is 

 only observed so far as the flood tide rises. 



The author found in the mud taken out of the Ems, three- 

 quarters of a league below Weener, and about forty miles from the 

 North Sea, thirty-seven species of siliceous-shelled Polygastrica, 

 and nineteen species of calcareous-shelled Polythalamia, most of 

 which are the same as those found in the Elbe. The list, how- 

 ever, contains nine new species of Polygastrica, and eight of 

 Polythalamia. One of the Polygastrica constitutes, indeed, a new 

 genus, and is particularly interesting as illustrating the nature of 

 fragments found in the chalk marl of iEgina, and described in a 

 former paper. In the mud of the Dollart from the harbour of 

 Emden, most of these forms also occurred together with Miliola 

 ovum and Rotalia egena. 



In the pure sea mud from Nordeney, the above described species 

 of the Elbe, the Scheldt, and the Ems were most abundant, and 

 were associated with a few peculiar and partly new forms. On 

 the whole, there were twenty-eight species of Polygastrica, and 

 nine of Polythalamia. Almost the same species occur again in 

 the mud of the Jahde, near Hocksiel in Jeverland. 



All these mud deposits are quite superficial, and form the upper 

 bed of the bottom of the sea, and, like drift sand, sometimes form 

 islands above the action of the tides. The observations which have 

 been made to a greater depth had, however, produced very in- 

 teresting results, similar to those which have been already obtained 

 near Gliickstadt. 



In Jeverland, at a depth varying from 15 to 29 feet under layers 

 of earth called Watt-sand and Kiel (wet or quick sand, and clay), 

 there is often found a black elastic bed 1 or 2 feet thick, known 

 by the name of Darg. Piles driven 28 or 29 feet deep into the 

 sand are checked on this elastic layer, but on breaking through 

 it, are easily driven 12 or 18 feet deeper, Avithout further check. 

 This formation, according to Herr von Thiinen, occurs in almost 

 all the marsh lands between Jutland and Friesland, as well as in the 

 English marshes far outside the present dikes, and a more accurate 

 knowledge of this substance is greatly wanted, and is necessary 

 for the proper understanding of the earliest formation of these 

 marshes. The author had, in former years, observed a similar 

 condition in the Baltic, near Wismar, where on the island Lang- 

 Ort, near Pohl, a turf-like submarine substance in cakes of the size 

 of a hand, is broken off and thrown on the north shore of the 

 island, and is easily recognised as a half-dried mass, containing 

 numerous microscopic marine animalcules. 



The Darg of East Friesland, taken from a depth of 15 feet, ex- 



