Palaozoic Geology. 557 



name for the types he had worked out, will not permit the labours 

 of his friend to be submerged, and thus seem to convey to foreign 

 •Geologists the idea, whidi is indeed far removed from the truth, that 

 there are any real differences between his views and my own on this 

 important subject. In terminating these considerations, I beg geo- 

 logists to recollect, that I never entertained the idea that the local 

 types around Ludlow and Wenlock would be found applicable in 

 detail to strata of the same age in distant places ; on the contrary, 

 having shown that even within a very limited radius such subdivi- 

 sions varied with varying conditions, it was a leading and constant 

 object of my work, to demonstrate that the broad divisions of Upper 

 and Lower Silurian alone, could be maintained as terms of distant 

 and foreign comparison. 



There are two short communications by Mr. Lyell on the older 

 rocks to be noticed. The first is on the strata between Aymestry 

 and Wenlock, in which he dwells on the assistance to be derived 

 respecting the amount of dislocation in strata, by attentively no- 

 ticing the deviation from a vertical position of the inclosed corals ; 

 but he adds that great caution should be used to distinguish between 

 those specimens which may have been torn from their position with 

 reference to the horizon while growing and inverted, and those which 

 have lost their original mode of growth by subsequent dislocation of 

 the strata. From the known habits of recent corals, Mr. Lyell also 

 infers that the Silurian strata must have undergone successive de- 

 pressions during their accumulation, as beds of Polyparia belonging 

 to the Wenlock limestone are overlaid by many hundred feet of 

 sedimentary matter. In the second communication Mr. Lyell offers 

 some remarks on a series of fossils from the neighbourhood of Chris- 

 tiania, and he infers from the evidence they afford, that the lime- 

 stone to which they belong is of the age oft he Lower Silurian rocks ; 

 and on similar grounds he places the limestone of the island of Lan- 

 goen, one of the highest beds of the country, in an intermediate 

 position between the upper and lower Silurian rocks, constituting 

 a jjassage from the one to the other. 



The last memoir which has been read before us on the British 

 Palaeozoic rocks, relates to their development in a part of West- 

 moreland, and is from the pen of Mr. D. Sharpe ; and I rejoice to 

 see so clear and systematic a workman enlisted in the survey of the 

 older rocks. Agreeing on some essential points with Professor 

 Sedgwick and Mr. James Marshall, particularly in reference to the 

 superior and inferior limits of the Upper Silurian group, this author, 

 who liad previously made himself acquainted with the best types of 

 the Silurian rocks, conveys to us additional details of this interesting 

 tract, in which he has distinguished upon a map the Upper Ludlow 

 rocks, as characterized by many fossils, from an inferior slaty for- 

 mation which lies between them and calcareous bands charged with 

 Lower Silurian fossils. Dividing tiiis intermediate formation into 

 three sub-groups (by only mineral cliaractcrs however), he gives to 

 the whole the local name of " Windermere Rocks,"— a term which 

 I understand he only uses until by the discovery of fossil evidences 



