489 



to have lived near the shore, and belonging to genera formerly re- 

 garded as foreign to the carboniferous limestone, such as Isocardia, 

 Nucula, Pecten, Patella, Turritella, and Buccinura. Many species 

 of Zoophytes and Crinoidea are also described and figured in this 

 excellent monograph. 



We are indebted to Mr. Austen for a description of the South of 

 Devonshire between the river Ex and Berry Head, and between the 

 coast and Dartmoor, a district consisting of transition rocks, new 

 red sandstone, greenstone, and trap. His speculations on the origin 

 of the different formations and the causes which gave rise to the 

 existing features in the physical geography of the country display 

 much talent and are full of instruction. 



The structure of Devonshire has also furnished a fertile fieldof in- 

 quiry to Messrs. Sedgwick and Murchison since our last Anniversary. 

 They have attempted the difficult task of establishing a classifica- 

 tion of the older rocks so largely developed in that county. In every 

 geological map hitherto published of Devonshire, all the stratified 

 deposits of higher antiquity than the new red sandstone had been 

 represented by one common colour, the limestones being all included 

 as integral parts of one great formation called greywacke*. But 

 these gentlemen, after examining this region, announced at Bristol 

 to the geologists assembled at the Meeting of the British Association, 

 that the great mass termed greywacke, and previously undivided, 

 comprised in it several formations of great thickness, ranging in 

 age from the Cambrian system of Professor Sedgwick up to the 

 true carboniferous series inclusive. The first groups mentioned by 

 them in ascending order are the Cambrian and Lower Silurian,- 

 which great mass contains many distinct courses of limestone ; and 

 is separable into several formations, distinguishable from each other 

 by stratigraphical position and by lithological and zoological cha- 

 racters. 



There appears, however, to be a great hiatus in the succession of 

 rocks in Devonshire, as compared to South Wales, there being no 



* The Abstract of the Report of Messrs. Sedgwick and Murchison, pub- 

 lished with a section in the Athenaeum, August, 1836, and in other scientific 

 journals, is the same as that written for insertion in the Proceedings of the 

 Association. From that document, and from a written explanation of their 

 views, which I obtained from the authors, the present observations are de- 

 duced. 



