J. H. Cooke — Globigerina Limestones of Malta. 



503 



Bed A. — The "Marls and Clays" that overlie this formation 

 graduate downwards into a close-textured, fine-grained freestone, 

 the upper portion of which contains from 25 to 30 per cent, of 

 alumina, but towards the lower part this percentage decreases 

 until the ratio of alumina to calcium carbonate is as 1 to 9. The 

 bed is variously coloured, the upper layers being generally of 

 a bluish-grey, and the lower part of a light-yellow or yellowish- 

 ashen colour. Iron pyrites abound, and it is to the decomposition 

 of these that the tinctorial variations are due. Organic remains 

 are plentiful, but as a rule they are so pseudomorphed with either 

 peroxide or phosphate of iron, as to be barely recognizable. The 

 carbonate of lime, of which the shells were originally composed, 

 has been wholly or partially replaced by carbonate of iron, and 

 this, by subsequent oxidation, has been converted into a hydrous 

 peroxide. The pyritized condition of the fossils is a feature of this 

 bed. The most prevalent and characteristic forms are Aturia aturii, 

 Pecten Koheni, Pecten denudatus, Chenopits pes-pelicani, Dolichotoma 

 cataphracta, Nuculana fragilis, and Marginella Deshayesi. Many 

 forms of the Gorgonidae, 1 e.g. his Peloritana, I. Melitensis, and 

 I. compressa ; the claws and carapaces of Cancer macroceplialus ; and 

 the tests of pteropocls, chiefly VagineUa and Hyahe, invested in 

 thin metallic-iron coverings, are also numerous. 



The Scalarice* which make their first appearance in division F, 

 and are continued in the successive beds up to the " Marls and 

 Clays," are here represented by the minute form S. Melitensis, Fuchs. 



1 For the determination of the Gorgonidae I am indebted to Professor Angelli, 

 Universita di Roma. 



2 Mr. G. F. Harris, F.G.S., kindly determined the Scalarice 



