ANI^IVERSAEY ADDRESS OP THE PRESIDENT. Ixiii 



The fauna of the Mediterranean naturally presents a consi- 

 derable difference from that of the Atlantic, especially from that 

 portion which inhabits the greater depths of the latter. There is 

 an absence of the numerous recent arctic forms which foUow the 

 cold currents of the Atlantic, although there are many northern 

 forms of Quaternary and PUocene age, which seem to have been 

 introduced into the Mediterranean area at a period when the com- 

 munication between the two seas may have been more open — an 

 inference made by several observers both on natural-history and 

 on geological grounds. Newer Tertiary strata extend, in fact, a 

 great part of the way across from the Bay of Biscay to the Medi- 

 terranean, and the watershed between the two seas is not higher 

 than about 600 feet above their levels. At one point on this line, 

 and at an elevation of 560 feet above the Mediterranean, M. Yirlet 

 d'Aoust many years since discovered, in a fossil state, the Ostrea 

 hipjpopus and Murecc trunculus, species still living in that sea. 



Erom these considerations the question arises whether the deep 

 sea in which the Chalk, with its more tropical genera, was de- 

 posited, may not also have been a sea shut out from direct com- 

 munication with Arctic seas. The Old and New continents have 

 a north and south extension, with intervening oceans in the same 

 direction ; but the distribution of land and water must have been 

 very different during the Cretaceous period. Beds of this age stretch 

 from England through France, Germany, Poland and Southern 

 Eussia to Persia and India, and they also traverse the southern 

 portions of the North- American continent. Throughout much of 

 Europe and parts of Asia the Chalk has the common character that 

 it possesses in England, and which has led it to be likened to the 

 Atlantic deep-sea mud. On the other hand, there is no Chalk north 

 of Denmark, in North Russia or Siberia, or in Arctic America. If 

 the direction of the deep Chalk-ocean followed this east and west 

 belt across the present continents, then we must look for dry land 

 on the confines of that ocean ; and it is probable that the latter 

 may have been, to the north, in the direction between Greenland 

 and Scotland and Scandinavia, where the present ocean is some 

 hundreds of fathoms shallower than further south. We know 

 that towards the end of the Cretaceous period, a change took 

 place in the fauna, arising apparently from the shallowing of the 

 sea that preceded the deposition of the Maestricht beds, as well as 

 of the Calcaire pisol'Uique of Laversine and Mont Aime. Many 

 of the great Cephalopods disappeared, and reptiles increased in 



