F. Chcqynian — Egi/pt'um Fomminifera. 3 



II. — On A PATELLiy.i - LIMESTONE AND ANOTHER FoRAMINIFEBAL 



Limestone from Egypt. 



By F. Chapman, A.L.S., F.R.M.S. 



(PLATE II.) 



THE specimens dealt with in this paper were collected by the 

 Officers of the Geological Survey of Egypt, and I have been 

 requested by Dr. H. Woodward, on behalf of Captain H. G. Lyons, 

 R.E., F.G.S., the Director-General, to give an account of the various 

 species of Foraminifera met with during the progress of the Survey. 



The P^7'£'X£/ivr^-LIMEST0NE. 



These specimens bear the Survey label No. lie (827). The rock 

 occurs on a plateau between Cairo and Suez, the geological position 

 of which Mr. Barron is inclined to consider as the base of the 

 Miocene grits and marly clays (letter dated 29th July, 1899). 

 The exact locality whence these samples came is situated six kilo- 

 metres west of Camp 35, in lat. N. 30° 17' 55", long. E. 32° 18' 14". 



The rock is of the greatest interest on account of the presence of 

 a new species of PatelUna, which constitutes a large proportion of 

 the limestone. The relative abundance of the Patellinm iu the rock 

 can be well seen in the photograph (PI. II, Fig. 1) of a thin section 

 taken haphazard from the rock-specimen. This genus appears to be 

 hitherto quite unknown in the limestones of Egypt. 



Besides Patellince there are other foraminifera associated with it in 

 this rock, belonging to the genera Biloculina, MilioUna, Orhiculina, 

 AlveoUna, Bigenerina, Discorbina, Truncatidina, Gypsina, Polytrema, 

 and Nonionina. 



The limestone is ochreous-yellow to pale brown in colour. The 

 matrix of the rock is somewhat spongy, cavities caused by chemical 

 solution and recrystallization being seen here and there, whilst in 

 section the foraminifera other than the Patellince frequently have 

 a space between the wall of the test and the matrix by which it is 

 partially filled. When the rock is crushed for the extraction of the 

 smaller organisms the casts fall out, leaving the walls of the tests 

 adhering to the matrix. 



The microscopic structure of the enclosing rock-mass is distinctly 

 crystalline, which condition is probably due to subsequent molecular 

 disturbance of the calcareous mud in which the foraminifera were 

 embedded, and which has resulted in the formation of a granular 

 calcitic material, in which scalenohedra are an abundant crystalline 

 form, especially on the borders of the cavities. 



Besides foraminifera there are some obscure examples of polyzoa. 

 An ostracod (Bairdia, described below) also occurs in some numbers, 

 represented both in section and by a specimen isolated from the rock. 



Scattered through the rock are some rounded grains of quartz 

 averaging 1 mm. in diameter, and often containing strings of 

 minute inclusions or gas cavities. 



