51. Peridinium pyropho- 1 „ i.- v i 



j.jjjjj '^■' * >■ Baltic, near Kiel 



52. Striatella arcuata , 



53. Synedra ulna 



on the Organic Composition of Chalk and Chalk Marl. 455 



Living. Fossil. 



{Flints of the W. C. near 

 Gravesend, and Flints 

 of the plain of North 

 Germany near Delitzsch. 

 J Gulf of Flensburg, Break- 1 . 

 ■ \ ers near Gothenburg. J 

 ' Baltic near Wismar, Ber- 

 lin fresh waters, North 

 of Germany, Denmark, 

 Scotland, Holland, the 

 Ural, and perhaps Isle 

 of France, and Masca- 



rene Isles ^ 



Breakers near Gothen- 1 . 

 burg and Berlin waters. J 

 65. Triceratium Favus . . North Sea, Cuxhaven . . CM. Greece. 



Flints of W. C. Graves- 



S6. Xanthidium furcatum Berlin \ end, and Flints of 



Delitzsch. 

 Flints of W. C. Graves- 



57. hirsutum .... Peat waters near Berlin. ■^ end, and Flints of 



Delitzsch. 



54. Tessella Catena 



C. M. Oran. 



C. M. Oran. 



C. M. Caltasinetta. 



lin..^ 



Of these fifty-seven species, thirty belong to the geolo- 

 gically acknowledged chalk and its Sicilian marls. The re- 

 mainder from Oran, Greece (probably Egina), and Zante, 

 though perhaps from beds not equally well defined by relative 

 position as chalk marls, yet occurring, as they do, with nume- 

 rous decided calcareous and siliceous animals of the chalk, — 

 the geological relations of these species may also be considered 

 as firmly established. 



These new discoveries naturally lead to the conclusion that 

 we have now no very definite boundary between secondary 

 and tertiary tracts, and that the first dawn or eocene period 

 of the present living organic creation, must be sought for 

 deeper than the chalk formation; a view that appears to be 

 confirmed by the occurrence of a living TrocJius below the 

 chalk, of the Paludina vivipara and Cyclas cornea in the 

 Weald Clay, and of the Terebratula captd serpentis in the 

 Upper Oolite. But as this and other interesting conclusions 

 and views entertained by the author will be shortly laid open 

 to the reader, with a full detail of the progressive researches 

 made, 1 shall not now enter further upon the important mat- 

 ter contained in the volume. 



