Vol. 67.] THE GEOLOGY OF CYRENAICA. 593 



Near Benghazi the lower limestones have sunk beneath sea-level, 

 and the beds exposed around the town are recent dune-limestones 

 containing common Mediterranean shells, such as Glycymeris 

 glycymeris (Linn.), Codakia pecien (Lam.), Ostrea edulis (Linn.), 

 Cheliconvs mediterraneus (Hwas), etc. Behind the dune-limestones 

 and the dunes to the north of the town are wide sheets of alluvium, 

 which has been deposited in lagoons that are still flooded at intervals 

 and used as salt-pans. 



IV. Classification and Correlation of the Cyrenaican 

 Rocxs. 1 (Continued on p. 598.) 



The field evidence, including a preliminary determination of 

 some Echinoids, suggested during the traverse of Cyrenaica the 

 following classification of the rocks : — 



Pleistocene. Various alluvial deposits, coastal limestones, etc. 



,,- . f Scutella Limestones, east of Benghazi, and Gubah-Birlibah 



\ Limestones. 



f Cyrene Limestones (Aquitanian). 

 Lower J Slonta Limestones. 



Kainozoic. 1 Derna Limestones. 



t Apollonia (chert-bearing) Limestones. 



The most surprising geological result of the journey was the 

 comparative rarity of Miocene beds. They are so well developed 

 in Western Egypt, as at Siwa and on the coast near Mersa Tobruk, 

 that the prevalent opinion in recent years (see p. 576) had been 

 that Cyrenaica was mainly composed of Miocene rocks. The 

 subsequent study of the collections has, however, even lessened the 

 area that in the field I was disposed to assign to the Miocene, as 

 the species of Amphioj^e, a genus especially found in that system, 

 has to be referred back, owing to its associated fossils, to the 

 Eocene. 



The correlation of the rocks of Cyrenaica depends upon the 

 fossils, mainly mollusca, foraminifera, and echinoids, upon which 

 reports have been prepared by Mr. R. B. Newton, Mr. E. Chapman, 

 and myself. 



The oldest rocks exposed occur in the Tokra fault-scarp, east 

 of Benghazi ; they are somewhat lower than the chert-bearing 

 limestones, but no determinable fossils were obtained from them. 



1 Owing to the varying nomenclature of the Middle and Lower Eocene 

 Kainozoic Series, the following synopsis may be convenient for reference : — 



T Tortonian 1 



Miocene < Helvetian; 



[Burdigalian or Langhian. 



{Aquitanian (often included in the Miocene). 

 Stampian or Rupelian 1 Tongrian (sometimes used to 

 Sannoisian or Ligurian J include Stampian). 

 ( ( Priabonian or Ludian (sometimes included in the 



! Upper. \ Oligocene). 



-p, J [Bartonian. 



eocene <; Middle> p ar i 3um (Lutetian) ; Mokattam Series of Egypt. 

 | j , f Londonian or Ypresian ; Libyan Series of Egypt. 



i^ ' \ Suessonian, Thanetian or Landenian. 



