Reports & Proceedings — Geological Society of London. 287 



9. On Pkimary Analcite and Analcttization. By A. Scott. 

 Trans. Geol. Soc. Glas., xvi, p. 34, 1916. 



IX this paper Dr. Scott traces the history of the controversy that 

 since 1«90 has centred about the origin of analcite in igneous 

 rocks. He summarizes first the arguments against the primary 

 nature of the mineral and secondly the evidence in favour of that 

 view. It is pointed out that there are three ways in which rocks 

 may be modified by the action of alkali material : — 



1. During an early stage in the cooling history of a magma, the 

 liquid residuum becomes enriched in sodium-bearing molecules, so 

 that the later portions of the pyroxenes and amphiboles are relatively 

 enriched in that element. 



2. At a late stage in the cooling history, phenocrysts already 

 formed may be corroded by the soda residuum ; felspars and nepheline 

 are analcitized and any residual analcite that remains crystallizes 

 out as a primary mineral. 



3. At a period subsequent to consolidation the rock may be acted 

 on by juvenile soda-silicate solutions in such a way that felsic 

 minerals are analcitized, while mafic minerals may be recrystallized 

 as soda pyroxene. 



REPORTS .AJSTID PROCEEDINGS. 



Geological Society of London. 

 1. May 2, 1917.— Dr. Alfred Harker, E.E.S., President, in the Chair. 



The following communications were read : — 



1. " Supplementary Notes on Aclisina, De Koninck, and Aclisoides, 

 Donald, with Descriptions of New Species." By Jane Longstaff 

 {nee Donald), E.L.S. (Communicated by Dr. G. B. Longstaff, M.A., 

 F.G.S.) 



Since the publication of a paper by the Geological Society on 

 Aclisina, in 1898, a much larger amount of material has come to 

 hand, which has not only added to the knowledge of the species 

 there described, but has also led to the discovery of six others new 

 to science. The diagnoses of these are now given, and a species 

 named by Mr. H. Bolton Loxonema ashtonensis is referred to this genus, 

 as several specimens show the characteristic lines of growth. 



The total number of species of Aclisina is now brought up to 

 twenty-two, and there are besides several varieties. The genus is 

 best represented in Scotland, where the specimens are generally 

 remarkably well preserved, no less than thirteen having the 

 protoconch intact, drawings of which show its somewhat irregular 

 character. A table is appended giving, so far as known, the range 

 and localities in the British Isles and Belgium. A small variety of 

 Aclisina pulchra, De Koninck, appears to have continued for the 

 greatest length of time, commencing in the Calciferous Sandstone 

 Series, existing throughout the Lower and Upper Limestone Series 

 and on into the Millstone Grit of Scotland. 



Additional observations are also made on Aclisoides striatula, 

 De Koninck, showing its variation in size and ornamentation, 



