246 MR. A. W. WATERS ON FOSSIL LITHOTHAMNIA. 



Since then Giimbel has published, in 187 1, an excellent 

 monograph* on the fossil forms, under the title "Die so- 

 genannten Nulliporen," in which he establishes fifteen 

 species. This paper has been largely used in preparing 

 the present notes. 



This would seem to be the best place to mention their 

 importance in geological formations. As most present 

 will know, they attain their greatest development in the 

 Leithakalk, a Miocene formation, which is principally, 

 in some cases almost entirely, composed of this Alga. 

 Unger says he has never seen any which contains less than 

 two thirds. Thus formations of vast extent and many 

 hundreds of feet thick, perhaps in some places thousands, 

 are largely composed of this limestone seaweed. But it is 

 in no way confined to the Leithakalk, being also very 

 abundant in the Eocene, especially the upper divisions; 

 the so-called " Granitmarmor," or Bavarian marble, a 

 Nummulitic formation, is very largely composed of this 

 concretionary-looking body. From what I have seen, I 

 should judge that more than half is thus made up. 



This is a very good building-stone, largely used in 

 Bavaria. In all the large buildings in Munich (as the 

 Glyptothek, Pinakothek), and many of the buildings at 

 Vienna, this marble is extensively used. In North Italy 

 it abounds in the Eocene formations which are so largely 

 developed in the Veronese and Vicentin. Some of the 

 pieces before you will show what a large proportion some 

 of the rocks there contain. In many places the formation 

 is some hundred feet, much more than half composed of 

 the Lithothamnium. 



It occurs abundantly in Hungary and Switzerland. The 

 so-called Pisolithic limestone of Paris is, according to 

 Giimbel, about four fifths stone Algse, also Monte Mario, 

 Astrup, the Pliocene of Castel Arquato ; and, in fact, it 



* Abhand. d. k. bay. Ak. der Wissensch. xi. part i (Munchen, 1871). 



