406 Notices and Extracts from the Minutes of the Geological Society. 



the most northern spot hitherto observed. It is formed of two walls of green- 

 stone, each from two to four feet in thickness ; and these walls contain between 

 them a breccia, composed of fragments of shale and whin, cemented by calca- 

 reous and argillaceous matter. Carburetted hydrogen and pure water issue 

 from a narrow fissure in the broadest part of the dyke. The coal of the beds 

 through which the dyke passes is charred, and deteriorated in quality, to the 

 distance of about forty yards on each side. 



3. — Extract of a Letter from Charles Stokes, Esq., P.G.S. F.R.S. &c., to 

 William John Broderip, Esq., Sec. G.S., F.R.S., &c.; explanatory of 

 three Drawings of Echini. [Read June 20th, 1829.] 



1. A specimen of Galerites albo-galerus * (Lam.) from the chalk, in which 

 the plates of the mouth, consisting of five pairs, are preserved in situ : — 2, A 

 Cidaris f also from the chalk, in which portions of the plates of the mouth and 

 teeth are visible; — they are displaced, but exhibit a system quite analogous to 

 that of the recent Cidaris : and 3. A Cidaris;}; from Stonesfield, in which the 

 anal plates are in the best preservation. 



* Plate XLV. fig. 14 & 15. + Plate XLV. fig. 16. t Plate XLV. fig. 17. 



