624 MU. R. B. NEWTOK ON [Nov. I9II 



Mediterranean and Atlantic species. In post-Pilocene deposits it 

 has been recognized by d'Archiac from Greece, 1 by P. Fischer 

 from Asia Minor, 2 by M. G. Holland from localities in Algeria, 3 by 

 Dr. Blanckenhorn in the neighbourhood of Alexandria, 4 by M. Bede 

 from Tunisia (Sfax), 5 by Messrs. Bellamy & Jukes-Browne from 

 Cyprus, and by Dr. Pachuudaki from near Mersa Matruh on the 

 Marmarican plateau of Northern Africa. 7 



Occurrence. — The shells are associated with a compact cream- 

 coloured limestone, and sometimes with a soft, pale, marly-looking 

 rock ; an external tinge of reddish brown, the result of weathering, 

 etc., is observed on most of the specimens. The small brackish- 

 water gastropod Paludestrina { = Hydrohia) occurs in the same 

 matrix with these specimens. 8 



Locality. — Plain east of Benghazi. 



1 In Viquesnel's ' Voy. Turquie d' Europe ' 1855, vol. ii, pi. xxiv, fig. 7 & p. 479. 



2 In P. de Tchihatcheff's ' Asie Mineure' pt. iv (1806-69) p. 856. 



3 'Geologie du Sahara Algerian — Cheinin de Fer Transsaharien ' French 

 Government Report [Paris] 1890, pi. xxviii, figs. 20-21 & pp. 158, 194, etc. : 

 both solid and fragile examples. 



4 'Neues zur Geologie & Paliiontologie iEgyptens — IV. Das Pliocan- & 

 Quartarzeitalter' Zeitschr. Deutsch. Geol. Gesellseh. vol. liii (1901) p. 466. 



5 Bull. Mus. Hist, Nat. [Paris] vol. ix (1903) p. 423. 



6 ' The Geology of Cyprus' 1905, p. 51. 



7 ' Contrib. Geol. Marsa Matrouh (Marmarique) ' 1907, pp. 4 & 6. 



s [Since the reading of this paper, a re-examination has been made of the 

 limestones containing Cerastoderma edule which Prof. Gregory obtained from 

 ' Plain east of Benghazi.' They exhibit a number of small gastropods and 

 fragmentary pelecypods which areof importance to include in this accountof the 

 fossil shells of Cyrenaica. The most frequently occurring genus is Paludestrina ; 

 there are also aBulimuloid shell, another resembling a Helicoid, a possible Trun- 

 catella, Nassa (?), fragmentary Cerithium like vulgatum, and some imperfect 

 valves of probably Telliniform shells. Such a fauna would suggest a brackish- 

 water origin, the deposition of the beds containing the same being due to 

 lagoon or estuarine agencies rather than to conditions involving true marine 

 characters. 



Bourguignat (' Pal. Moll. Terr. Fluv. Algerie ' [Paris] 1862, plates & text) has 

 described a somewhat similar association of forms from the post-Pliocene 

 formation of Algeria (the ' Ohotts ' of the Algerian Sahara) ; while Tournouer 

 (O. B, Assoc. Frang. Av. Sci. 1879, Sess. vii, pp. 608-22, pi. vi), who sub- 

 sequently studied the same area, was of opinion that the molluscan evidence 

 was against the existence of a marine submergence of that part of Northern 

 Africa during post-Pliocene times. There is another well-known instance of 

 the occurrence of Paludestrina with Cerastoderma edule presented by the 

 Aralo-Oaspian region of Western Asia, where these molluscs are found both in 

 the fossil and in the recent state. An interesting monograph has been published 

 by Mr. W. Bateson on variations observable in the valves of Cerastoderma 

 edule (Phil. Trans. Boy. Soc. London, 1890, vol. clxxx, pp. 297-330 & pi. xxvi), 

 which he regards as due to differences of environment more particularly con- 

 nected with the varied degrees of the salinity of the waters ; the material for 

 this work was collected by the author from the lake-regions of Northern Egypt 

 (Mareotis, etc.), as well as from the Aralo- Caspian country. 



The limestones from ' Plain east of Benghazi' appear, therefore, to represent 

 two horizons: the oldest being Vindobonian and entirely marine, with Scutella, 

 Pecten zizinice, fora,mimt'er&,&ndLithotha??inion ; the youngest showing brackish- 

 water characters from the presence of Cerastoderma edule, Paludestrina, etc., 

 which are recognized as belonging to an ancient part of the post-Pliocene 

 formation.] 



