New Bracliiopod fror)i the Kuclcers Stage hi Estonia. 361 



has disappeared ; the few ferro-Biagnesian constituents are more 

 evenly distributed, and have a tendency to form irregular broken 

 bands. They consist mainly of uralite and chlorite, apparently 

 after a rhombic pyroxene. The outer edges of many of these 

 pseudomorphs consist of a strongly pleochroic dark mica. The 

 absence of primary mica and amphibole is conspicuous. The small 

 basic patches consist of badly weathered felspars, quartz, fibrous 

 amphibole and chlorite, much finer in grain than the surrounding 

 groundmass. Surrounding these basic patches is an envelope of 

 interstitial quartz. This envelope is more pronounced than that 

 which surrounds the basic aggregates in the granophyric rock. 



IV. Conclusions. 



Both the grr.nitic and the granophyric types described above 

 apparently belong to the same rock mass, as an examination of the 

 laccolith in the field affords no evidence which suggests that it was 

 not formed from a single intrusion. R. H. Rastall ^ describes and 

 discusses in detail the occurrence of a micropegmatite within an 

 intrusive mass, and an outward transition to a normal granitic 

 rock ; and as far as the leucocratic constituents are concerned, the 

 Llwydmor Bach Granophyre forms a parallel to the Buttermere 

 and Ennerdale Granophyre. 



Chemical analyses are not yet available, but a microscopic 

 examination reveals the fact that the micropegmatite is more 

 basic than the granite. This higher basicity of the interior of the 

 laccolith is due to the presence of the " clots " of pyroxenes and 

 amphiboles. These basic patches are presumably cognate xenoliths 

 which are relatively undisturbed m the well-developed micro- 

 pegmatite. There is a tendency for these basic aggregates to be 

 distorted with a diminiition of the monoclinic pyroxene as the rock 

 approaches the margins of the laccolith. 



The Llwydmor Bach Granophyre is apparently an intratelluric 

 hybrid, an acid rock, which had become impregnated with a solidified 

 basic magma, or had the dregs of a partially solidified local magma 

 reservoir injected with the still liquid acid portion. 



A New Brachiopod (Leptestia) from the Kuekers Stage 



in Estonia. 



By Hendrik Bekker, Ph.D. (London). 



A MONG the Brachiopoda described in my recent memoir on the 

 •^ Kuekers stage of north-east Estonia, there was an undetermined 

 member of the Stropliomenacea, of which the interior of the dorsal 

 valve was unknown. I have since found a dorsal valve with its 

 exterior (concave) outwards, embedded in kuckersite. By filling the 

 concavity with plaster of Paris the shell could be easily removed 



1 R. H. Rastall, Quart. Journ. Geol. Soc, vol. Ixii, 1906, p. 253. 



