18 SCIENCE PROGRESS. 



CALCAREOUS ALG^E OF THE CLASS FLORIDE.^. 



The Miocene Leithakalk of the Vienna Basin has long 

 been quoted in text-books as a rock largely composed of 

 the genus Lithothamnion. This characteristic fossil was 

 originally described by Reuss as Nullipora ramosissima and 

 placed by him in the category of fossil animals. The genus 

 Nullipora has been used in an extremely wide sense, em- 

 bracing organisms which are for the most part members of 

 the vegetable kingdom, but including others which must 

 still be retained as animals. An important contribution to 

 the study of the Leithakalk appeared in 1858 by Unger. 1 

 He refers to the discovery by Philippi, in 1857, that several 

 of the so-called Nullipores had been erroneously included 

 in the animal kingdom, and goes on to describe in detail 

 the structure of Ntdlipora ramosissima from the Vienna 

 limestones. Unger gives descriptions and figures of the 

 genera Lithothamnion and Lithophyllum, and recognises the 

 important role of the fossil forms of these and similar algae 

 in the formation of limestones. 



The microscopic examination of the Leithakalk has 

 been considerably extended by Glimbel, who gives a number 

 of interesting facts as to the frequent occurrence of calca- 

 reous algae in limestones of different ages and localities. 2 



Specimens of Lithothamnion are described from Jurassic 

 rocks near Neukirchen, the Maestricht chalk, Pisolites of 

 the Paris Basin, etc. 



With a view to throwing fresh light on the geological 

 action of calcareous rock-forming algae, Walther availed him- 

 self of the facilities afforded by the Biological Station at 

 Naples to make a special study of living rock-building plants. 

 He examined the Secca di Chiaja, the Secca della Gajola 

 and the Secca di Penta palumno, and investigated the for- 

 mation of calcareous deposits at present in operation in 

 those submarine plateaux. 



The Secca della Gajola is described as a typical example 

 of a recent algal deposit ; it is situated about one kilo, from 

 the coast and 30 m. below the surface of the water. 3 



1 Unger. 2 Giimbel. 3 Walther (1). 



