484 



Geological Society. 



had captured a large Ichneumon, which wanted one of the posterior 

 tibiae and tarsi. 



Mr. W. W. Saunders exhibited some mud-nests sent from Alba- 

 nia by Mr. S. S. Saunders, and which had been formed by a species 

 of Pelopceus, which was thus proved to be a working and not a pa- 

 rasitic insect. Mr. Shuckard also mentioned, upon the authority of 

 Mr. E. Doubleday, that the American species of this genus are well 

 known as the fabricators of those mud-nests, and are thence called 

 Mud- dabs. 



Mr. W. W. Saunders also exhibited the larva of Cerambyoc heros, 

 which had completely eaten through a piece of timber, likewise ex- 

 hibited. 



GEOLOGICAL SOCIETY. 



From the Anniversary Address of the Rev. Prof. Buckland, 

 President, Feb. 21, 1840. 



DEVONIAN SYSTEM. 



In the Home Department of Positive Geology, the most striking 

 circumstance has been an announcement by Professor Sedgwick 

 and Mr. Murchison of the conclusion to which they were led by 

 Mr. Lonsdale's suggestion in December 1837, founded on the inter- 

 mediate character of the fossils in the Plymouth and Torbay lime- 

 stone — that the greater part of the slate rocks of the south of Devon 

 and of Cornwall belong to the old red sandstone formation. 



The order of the observations which have led to this important 

 result, is nearly as follows : — 



In a paper read at Cambridge, during the winter of 1836-37, 

 Professor Sedgwick considered the fossiliferous slates on both sides 

 of Cornwall to be of the same formation, and coeval, or nearly so, 

 with the calcareous rocks that lie between the slates of South 

 Devon. 



In 1836 and 1837 also*, Messrs. Sedgwick and Murchison pro- 

 posed to transfer the culmiferous or anthracitic shale and grits (Shil- 

 lot and Dunstone) of North Devon to the carboniferous system ; 

 withdrawing them from the grauwacke in which they had before 

 been included, and thus assigning a much more recent date than 

 heretofore to the strata which occupy nearly one third part of the 

 map of Devonshire. 



But the relations of the slates and limestones of South Devon still 

 remained to be determined ; the mineral characters of the former 

 being different from those of the old red sandstone beneath the car- 

 boniferous group, in many parts of South Wales and in Hereford- 

 shire, while the true position of the limestones (e. g. those of Ply- 

 mouth, Torbay, and Newton Bushell,) was doubtful. At this period 

 (1837), the fossils of this district were examined by Mr. Lonsdale 

 and Mr. Sowerby, to whom the organic remains, both of the car- 



* In August 1836, at the Meeting of the British Association at Bristol; 

 and in a paper read before the Geological Society, May and June, 1837, 

 now published in the Geological Transactions, Second Series, vol. v., Part 3. 



