5S8 DE. A. MOKLEl" DATIES OX THE EAUXAS [vol. Ixxix, 



In regard to the bulk of the two faunas, therefore, we have no 

 justification for considering their differences as of age-value : they 

 might be in part facies-differences, in part accidental differences of 

 collection. But, Avhen we come to consider certain definite species, 

 the case is different. At Minihagalkanda only we find two well- 

 marked forms not on the lists of A. d'Archiac or Sower by — Ostrea 

 virleti Deshayes, and an abnormally thick Pinna (.P. pachyostraca 

 sp. now) ; while at Kirimalai and other localities in the northern 

 half of the island, but not at Minihagalkanda, we find Orbiculina 

 malabarica Carter. 



Ostrea virleti is a well-marked species with a remarkable geo- 

 graphical distribution. It was first found (Deshayes, 1836) north 

 of Methone in the south-western corner of the Peloponnesus; but 

 its exact horizon there cannot be stated. Bertrand & Kilian (1889) 

 record it from Saleres in the South of Spain, dating it as Helvetian. 

 At Eregli on the northern coast of the Gulf of Xeros, in Thrace, it 

 was recognized bj Mr. It. B. Newton (1901) as Vindobonian. On 

 the south side of the Mediterranean it was found by Prof. J. W. 

 Gregory (1911), in the post-Acpiifcanian Miocene limestone at the 

 Caves of Lethe, Cyrenaica ; by K. A. von Zittel (1883) in the 

 Siwa Oasis ; and by the Egyptian Geological Surve}- through a 

 wide range of latitude on the western side of the Red Sea, and in 

 Sinai (Hume, 1916). In Armenia and Persia it has been recorded 

 at intervals from Avest of Erzerum to east of 55° long. E. (Oswald, 

 1912 ; Stahl, 1911). Dr. Oswald dates it in all cases as lowest 

 Tortonian ; but Stahl refers it to the Lower Mediterranean stage 

 (Burdigalian). All these localities, so far, come within the area of 

 the Miocene Mediterranean (though the form is unrecorded from 

 the Vienna Basin) ; but it has been lately discovered, on the one 

 hand bj Gregory (1921) as far south as Maunguja, near Mombasa, 

 and on the other by Pilgrim in the Lower Llinglaj or Talar Beds 

 of the Mekran coast (Yredenburg, 1911). The former of these 

 occurrences was apparently not in situ ; but in the latter it is 

 associated with a Gaj fauna, and Yredenburg at first assigned to 

 it a Burdigalian age, though in his latest paper (1921) he inclined 

 to a position as high as Pontian for the Talar Beds. 



In Burma O. virleti was described as O. pec/uensis by Ncetling 

 (1901), and present knowledge of its age in this region is summed 

 up as follows by Yredenburg (1921, pp. 2-31, 25S, 259) :— 



' 0. virleti and 0. digitata [digitalina] var. rohlfsii (Noetling's 0. pegu- 

 ensis and 0. promensis) occur together in the basal part of the Akauktaung 

 Series at Yethyauksan. [These beds are] probably the marine equivalents of 

 the Irrawadi Series — probably equivalent to the Talar stage of the Mekran 

 Series and to the Odeng Beds of Java ; or else mainly intermediate in age 

 between the zone of 0. latim,arginata and the Irrawadi Series, and, if so, 

 equivalent to the Nahan, to the Lower Manchhar, and in Java to the Tji 

 Lanang Series — either Pontian or Vindobonian.' 



Thus Ostrea virleti is one of the very few Miocene species that 

 appears to have lived in both the Mediterranean and the Indian 

 Ocean, and the beds in which it occurs have been ascribed to 



