Iviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



flora, that is, the most modern of the five floras, must have taken 

 place. 



I shall now endeavour to trace, in succession, the alterations in the 

 configuration of the land connected with each of the distinct floras; 

 geological changes, be it remembered, of a very modern date in 

 comparison with the elevations, subsidences, fractures and contor- 

 tions which produced the phaenomena exhibited by the older forma- 

 tions. 



The First, or West Irish Flora. — The author believes that during 

 the deposition of the Miocene tertiaries, a sea, probably shallow, 

 inhabited by an assemblage, almost uniform, of marine animals, 

 extended throughout the Mediterranean region, across the south of 

 France, along the west of Spain, and stretched beyond the Azores. 

 He founds this belief on the uniform zoological character of this sea, 

 from personal examination of Miocene fossils. He believes, that at 

 the close of the period, the whole of the bed of this Miocene sea 

 was pretty uniformly elevated in the region of the Central Mediter- 

 ranean and West of Europe. He then enunciates a new and some- 

 what startling opinion, viz. that "a great Miocene land,*" bearing 

 the peculiar flora and fauna of the type now known as Mediter- 

 ranean, extended far into the Atlantic,'past the Azores ; and calling 

 up botanical evidence in support of his views, he states that the 

 western boundary of this land, formed by deposits in the sea during the 

 Miocene period, but then an upheaved continent, is now marked by 

 the great semicircular belt of Gulf-weed, ranging between the 15th 

 and 45th degrees of north latitude, and constant in its place. He 

 adduces in support of this bold hypothesis, the testimony of Dr.Harvey 

 (whom he designates as one of the first of living authorities in ma- 

 rine botany) as to the nature of the Gulf-weed, the Sargassum hac- 

 ciferum, who considers it an abnormal variety of the Sargassum 

 vulgare, an opinion assented to by Dr. Joseph Hooker, who has had 

 great opportunities of studying the Gulf -weed. Now the Sargassum 

 vulgare, Professor Forbes says, is essentially a coast-line plant, 

 growing on rocks with a very limited vertical range ; and he believes 

 that the progenitor of the Gulf-weed was attached to the shores of 

 the post-Miocene continent, and that its present abnormal condition 

 is to be ascribed to the submergence of that ancient line of coast. 

 " The fact that there is a well-marked belt of Miocene coast-line in 

 North America, (as shown by Mr. Lyell,) and that the mollusca of 

 that belt indicate a representative, not identical, fauna in that region, 



* This term " a Miocene land " is equivocal, and is calculated to convey an er- 

 roneous idea of the author's meaning. It would have heen more correctly given 

 if he had said, a land consisting of rocks formed during the Miocene period, and 

 subsequently upheaved above the surface of the sea. There is a similarly ambigu- 

 ous expression used in a subsequent passage, where the author speaks of " a belt 

 of Miocene coast-line in North America," meaning a coast-line of rocks formed 

 under the sea during the Miocene period. A '' Miocene land," in correct geolo- 

 gical language, means land that existed during the Miocene period, on which the 

 land animals and plants then existing lived, and which bounded the sea and fresh- 

 water lakes in w4iich the aquatic animals and plants of that period lived ; and 

 such land might consist of rocks of any, and of several, antecedent epochs. 



