Vol. 67.] KAINOZOIC MOLLTJSCA FROM CYRENAICA. 651 



The occurrence of Pecten arcuatus and other associated mollusca 

 would suggest the presence of the Priabonian horizon. 



The late Prof. Rupert Jones's remark that the specimen of Num- 

 mulites perforata from Mersa Susa, one of the localities yielding 

 Pecten arcuatus of the present collection, was found in rocks which 

 were considered to be younger than the Nummulitic beds of Crete, 

 the latter being regarded as of Lutetian or Middle Eocene age, 

 is curious confirmation of the present results, the molluscan 

 evidence now determining the Priabonian horizon for these particular 

 deposits. 



The presence of Lutetian or Middle Eocene beds in Cyrenaica 

 seems also to be substantiated by the occurrence of the large 

 gizehensis type of Nummulites found associated in the matrix with 

 an indeterminable Ostrea. 



A. collection of well-preserved echinoids was also obtained from 

 the various formations in Cyrenaica, and they have been studied 

 by Prof. Gregory, with the general conclusion that their horizons 

 agree with those now suggested for the Mollusca. 



EXPLANATION OF PLATES XLIII-XLVI. 



[Except where otherwise specified, the figures are drawn of the natural size.] 



Plate XLIII. 



Hygromia sordulenta (Morelet). 



Post-Pliocene (recent beds). Bonmansur, south of Derna. (See p. 619.) 



Fig. 1. The upper or spiral view. X 2. 



2. Profile of the same specimen. X 2. 



Helicella tuberculosa (Conrad). 

 Post-Pliocene (recent beds). Plain east of Benghazi. (See p. 620.) 



Fig. 3. Dorsal aspect of the largest specimen. 



4. Front yiew of the same. 



5. Sculpture as seen on the penultimate whorl. X 3. 



Cerastoderma edule (Linnaeus). 

 Post-Pliocene (recent beds). Benghazi. (See p. 621.) 

 Fig. 6. External view of a left valve. 



Jagonia pecten (Lamarck). 



Post-Pliocene (recent beds). Benghazi. (See p. 622.) 



Eig. 7. External view of a left valve. X 3. 

 8. Sculpture details of the same. X 6. 



Cerastoderma edule (Linnaeus). 



Post-Pliocene (ancient beds). Plain east of Benghazi. (See p. 623.) 



Fig. 9. Left lateral view of a specimen covered anteriorly by a limestone 

 which is superficially pitted with minute rounded contiguous 

 excavations of probably organic origin. 

 10. Posterior end or ' escutcheon view ' of the same specimen. 



■Q. J. G. S. No. 268. 2 t 



