Brachiopods in the Persian Gulf. 45 
above. Its occurrence in this region has been remarked 
upon by several writers, including Davidson *, who regarded 
the locality as at fault. The present discovery of Mih/feldtia 
in the Persian Gulf adds further proof of the occurrence of 
the genus.outside the region to which it has hitherto been 
supposed to be restricted. 
The occurrence of two typical Lusitanian species of Brachio- 
pods in the Persian Gulf is of great interest from the point 
of view of geographical distribution. As pointed out by 
Schuchert T, “the present Mediterranean is the remainder 
of the ancient and far more extensive Tethys, always more or 
less in connection with the North Atlantic (= Poseidon), and 
in early Tertiary time communicating freely with the Indian 
Ocean.” A survey of the present distribution of certain 
groups of animals brings out very clearly that several forms 
have spread through this ancient Tethys. The Brachiopods 
are particularly interesting from this point of view. In 
addition to the two forms dealt with in this paper, others 
have been recorded from time to time, all of them pointing 
to an intimate connection between the Atlantic and Indian 
Oceans by way of the Mediterranean. In some cases the 
same species is common to both oceans ; in others, species of 
the Indian Ocean are closely allied to Atlantic forms. One 
of the most characteristic forms is the large Dyscolia wyvillet 
(Dav.), common on the east coast of the Atlantic from the 
Bay of Biscay to the Cape Verde Islands. It also occurs as 
a relict in the Antilles region. The same form is known 
from the Maldives, through the researches of Alcock, who 
described and figured the species under the name of Tere- 
bratula johannis-davisit. he Indian Ocean form has been 
carefully studied by Joubin $ and Blochmann ||, and. both 
consider it to be identical with the Atlantic species. In all 
probability it originated in ancient Tethys, as an ancestral 
form, Dyscolia (olim Terebratula) guiscardiana (Seg.), is 
found in the Pliocene of Sicily J. Chlidonophora is another 
genus having representatives in the Indian and Atlantic 
Oceans, and nowhere else. C. incerta (Dav.) is found off 
* Davidson, op. cit. pt. ii, 1887, p. 105. 
t+ Schuchert, “ Paleogeographic and Geologic Significance of Recent 
Brachiopoda,” Bull. Geol. Soc. America, vol. xxii. 1911, p. 271. 
ft Alcock, ‘Journal Asiatic Society of Bengal,’ vol. Ixiii. pt. ii. 1894, 
pp. 189-140. 
§ Joubin, Bull. de ’Inst. Océan. Monaco, no, 103, 1907, p. 6. 
|| Blochmann, op, ect. 1908, p. 688. 
4] Fischer and Oehlert, op. cit, 1891, p. 29. 
