92 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DcC. 1/. 



the general hypothesis with which they are associated, must be con- 

 sidered as always admissible, and can only be tested by observed 

 phsenomena. One remark, however, should here be made. The 

 periods of greatest cold in America and western Europe respectively 

 could not, according to this theory, be exactly synchronous. As- 

 suming, as we have done, the Gulf-stream to have existed during the 

 supposed changes of level of the North American and European 

 continents, it must have exerted its warming influence in the more 

 northern latitudes, either as a direct current along the flanks of the 

 Rocky Mountains, or as a reflected one on the western coasts of Eu- 

 rope. The cold due to the absence of its influence in both these re- 

 gions could not be strictly simultaneous, although belonging to the 

 same geological period. This is an essential conclusion of the theory. 

 I know not whether there are any geological facts which tend either 

 to favour or oppose it. 



36. It only remains for me to say a few words respecting the hy- 

 pothesis made in the early part of this memoir (art. 14, p. 68) of 

 the continuity of land from the north of Scotland to the coast of 

 Greenland. I have stated my opinion that the mean temperature 

 along such a northern shore of the Atlantic might be increased 4° or 

 5° F., and that the winter temperature would probably be much the 

 same on the coast of Iceland as in the latitude of central France. The 

 climatal change might possibly be still greater than here estimated. 



M. D'Orbigny has observed about a dozen species of subhttoral 

 molluscs in the West Indies, which he regards as identical with spe- 

 cies now inhabiting the western shores of the old continent in corre- 

 sponding latitudes. Now admitting the theory of the dispersion of 

 specific forms from single centres, this identity of species would 

 imply some connection between these localities on opposite sides of 

 the Atlantic, either by dry land or a shallow sea-bottom. I have 

 already stated (art. 32) the grave difficulty which besets the hypo- 

 thesis of a barrier of land across the Atlantic, and a similar difficulty 

 must attach to the hypothesis of a shallow sea-bottom. The conti- 

 nuity of the northern shores of the Atlantic warmed by the Gulf- 

 stream may possibly enable us to avoid the far more difficult hypo- 

 thesis just mentioned. I merely suggest this hypothesis, however, 

 for the consideration of those who may adopt the above opinion of 

 M. D'Orbigny, and draw from it the inference of a former connection 

 between the localities in which the identical species are found. 



3. Notice of the Discovery of Reptilian Foot-tracks and 

 Remains in the Old Red Sandstone of Morayshire. By 

 Capt. L. Brickenden, F.G.S. With « Description of the 

 Telerpeton Elginense, and Observations on Supposed 

 Fossil Ova o/Batrachians in the Lower Devonian Strata 

 o/ Forfarshire. By G. A. Mantell, LL.D., F.R.S., G.S. &c. 



[The reading of this Paper in full was deferred until the next Evening Meeting.] 



