Geological Society of London. 179 



stone, hippurlte limestoncj a lower tertiary conglomeratej the Almada 

 beds, and the upper tertiary sand. In the Memoirs of the Royal Acade- 

 my of Sciences of Lisbon, for 1831, Baron Eschwege had examined a 

 geological section taken across the mouth of the Tagus, and passing from 

 the granite of the Serra of Cintra, to that of the Serra of Arrabida. But 

 his identifications of the Portuguese beds do not agree with those of Mr 

 Sharpe, and have indeed the air of proceeding on the arbitrary assump- 

 tion of a correspondence between this and other parts of Europe. Thus 

 Baron Eschwege has referred both the San Pedro and the Espichel lime- 

 stones to the magnesian limestone ; the red sandstone-formation he con- 

 siders as Bunter Sandstein, while Mr Sharpe refers it to tlie age of our 

 Oolites : the hippurite limestone (now acknowledged to be the equiva- 

 lent of our chalk and grecnsand), M. Eschwege makes to be Jura lime- 

 stone ; and the Almada beds he would have to be Plastic Clay and Cal- 

 caire Grossier. Mr Sharpe is very properly attempting, by a further study 

 of the organic fossils which he has procured, to confirm or correct the 

 identifications to which he has been led. It is only by thus starting from 

 different points, and tracing strata by their continuity, that we can hope 

 to cover the map of Europe, and finally the world, with geological sym- 

 bols of a meaning fully understood. 



Palceontologi/. 



" The portion of our subject which we term Palaeontology might, at 

 first sight, seem to form a part of zoology rather than of geology ; since 

 it is concerned about the forms and anatomy of animals, and differs from 

 (he usual studies of the zoologist only in seeking its materials in the 

 strata of the earth's crust istead of upon its surface. Yet a moment's 

 thought shews us how essential a part of our science the zoology of ex- 

 tinct animals is ; for, in order to learn the history of the revolutions which 

 the earth has undergone, we must seek for general laws of succession in 

 the remains of organic life which it presents, as well as in the position 

 and structure of its brute masses. And since such general laws must 

 necessarily be expressed in terms of zoology, it becomes our business to 

 define those terms, so that they shall be capable of expressing truths 

 which include in their circuit the past as well as the present animal and 

 vegetable population of the world. 



" An example of this process has occupied a large portion of our at- 

 tention during the past year. It appeared to be a proposition universally 

 true, tliat the oldest strata of the earth's surface contained cold-blooded 

 animals only ; and that creatures of the class mammalia only began to 

 exist on tlie surface after the chalk strata had been deposited and ele- 

 vated. And when, to a rule of this tempting generality, a seeming ex- 

 ception was brought under our notice, it became proper to examine, whe- 

 ther the anatomical line, which enables us to separate hot-blooded from 

 cold-blooded animals, had really been rightly drawn ; and whether, by 

 rectifying tlic supposed characteristic distinction, the exception might 



