Microscopic Animals of the Chalk- Formation. 401 



Cocconcis oceanica, new species. 

 Shell elliptical, suborbicular, convex and very smooth on the back ; 

 marked exteriorly with simply curved concentric lines ; not undulated 

 nor transversely striated. Found at Callao by M. du Petit Thouars. 



II. Microscopic Animals of the North Sea. 



At the meeting of the Royal Academy of Sciences of Ber- 

 lin of the 13th August 1840, M. Ehrenberg communicated the 

 continuation of his researches on the numerous microscopic 

 animals of the chalk-formation which are still found alive. 



By the kind assistance of M. Berzelius, the author had re- 

 ceived some fresh sea-mud from the coast of Sweden, which 

 Bishop Eckstroem of Gothenburg had obtained for the pur- 

 pose from the Island of Tjoern in the Cattegat. This mud 

 proved to be extremely rich in new and interesting microsco- 

 pic animals. There are no less than twelve living species 

 which are of importance in a scientific point of view, and whose 

 siliceous coverings were only known in a fossil state in the 

 chalk-marls of Caltanisetta in Sicily, and of Oran in Africa ; 

 so that the number of species belonging to the chalk which 

 are found in a living state, is about doubled. A very inte- 

 resting fact is, the existence in a living state of the Gramma- . 

 iophora (formerly Navicula) Africana, which has hitherto been 

 known only as a fossil of the marls of Oran : and also that of 

 the oceanica, lately brought from Callao in Peru, and which 

 had previously been only met with in the marls of Greece. 

 M. Ehrenberg has likewise discovered in the waters of the 

 Cattegat a prismatic siliceous infusory form, which would be- 

 long to the genus Staurastrum, if it could be placed in the 

 subdivision of infusory animals having a soft carapace ; and 

 which, moreover, is distinguished by four large openings at 

 the four angles. It is proposed to form it into a new genus, 

 and to give it the name of Amphiletras antediluviana. There 

 was likewise found among the living infusory forms occurring in 

 the North Sea, one which is quite like the Dicti/ocha speculum, 

 but spinous like the Dictyoclia aculcata of Sicily. Finally, M. 

 Ehrenberg met with a series of eight species of the genus Ac- 

 tinocyclus, and of the radiated division without partitions 

 which form the great mass of the siliceous portion of the chalk- 

 marls of Caltanisetta, and still more of Oran, and which are 

 well characterized by the number of their rays. He detected- 



