278 Mr. S. V. Wood on the Form and Distribution of the 



long ago showed* the connexion of the American and European 

 miocene formations by the presence of several marine molluscous 

 forms in common. Now, the absence of any similar connexion 

 between the eocene marine mollusca of the two continents, while 

 so close a connexion exists between the terrestrial fauna of the 

 eocene of Europe with that now existing in America, seems 

 only intelligible upon the hypothesis of a land tract at once 

 joining the continents, but severing the seas. That this land- 

 connexion has been gradually disappearing since the eocene 

 period, is shown by the agreement among naturalists that the 

 molluscous fauna of the shores of the Western Isles, the Madeiras, 

 and of Portugal, affords evidence of the extension of Western 

 Europe in this direction between the miocene and the pleistocene 

 epochs, forming a province to which they have given the name 

 of Lusitanianf. 



The probability of the configuration, at the dawn of the tertiary 

 period, which I have described, receives support also from a con- 

 sideration of the climatal conditions which the fossils of that 

 period indicate. 



It has not unfrequently been remarked, as inconsistent with 

 any theory of a gradual refrigeration of climate during geological 

 periods down to the pliocene, that the eocene fauna of Europe, 

 both vertebrate and invertebrate, should at so late a stage in 

 the geological succession, present at least as tropical a character 

 as that presented by the fauna of any preceding stage in our 

 latitudes. The explanation of this fact, standing out as it does 

 at variance with any law of gradual refrigeration, should, I think, 

 be sought in a consideration of the geographical configuration 

 of the period. It is, with reference to this subject, also worthy of 

 remark that we do not find this tropical eocene fauna extending 

 up into high latitudes, as has been the case with the fauna of 

 more ancient deposits, as the carboniferous of Spitzbergen and 

 Melville Island, and even some of the secondary formations, 

 whose fauna in our latitudes presents perhaps a less tropical ap- 

 pearance than does that of the eocene. In seeking the expla- 

 nation of this tropical character of the eocene fauna of Northern 

 Europe, we may refer to the existing conditions of such gulfs as 

 the Arabian Sea and Gulf of Persia, the latter of which repre- 

 sents on a very small scale what I conceive the nummulitic gulf 



* Proc. Geol. Soc. vol. iv. p. 554. 



t See Forbes in ' Memoirs of Geological Survey of United Kingdom,' 

 vol. i. 1846, p. 406 & pi. 7, who indicates the land as far west as the me- 

 ridian of 30° W. See also Woodward, ' Rudimentary Treatise on Recent 

 and Fossil Shells,' Weale, London, 1856, pp. 361, 385. See also this view, 

 of the extension of the miocene land into the Atlantic, adopted, from other 

 considerations, by De Verneuil and Collomb, Bull. vol. x. p. 77 ■ 



