566 Notices of Memoirs — C Barrois — Fossils in ' J zoic' Mocks. 



of the granulitic rocks are those of segregation, and not of intrusion, 

 as many sections show these rocks associated togetlier in great 

 alternating bands with a concentric-like structure with complete 

 transition varieties, but with no sign of intrusion on the part of 

 eithei'. These concentric-like structures, which are certainly original 

 — due to cooling — have been subsequently displaced and broken up, 

 so that the now isolated portions are mistaken for intrusive tongues 

 of serpentine or included fragments of hornblende. When followed 

 out they resolve themselves into what were once connected masses. 



Wliile the main masses of these rocks have separated out from 

 each other, and cooled in the order of increasing acidity, there also 

 seems absolute proof in the field that the intrusive dykes in the 

 serpentine, consisting of diorite, granite, complexes of these and also 

 of gabbi'O, are but portions of the uncooled magma of the main 

 masses which were able to penetrate the serpentine. 



That the main masses and the dykes are of one and the same age 

 is evident, not only from their mineral composition and lithological 

 aspect, but also from the fact that all these rocks are inter-related — • 

 for example, the gabbro and diorite dykes coalesce, and dykes of the 

 former have margins of the latter. The diorite contains inclusiona 

 of gabbro, and in some instances inclusions of the latter contain 

 others of the former. The granulitic rocks, diorite, and gabbro occur 

 as a regular interbanded series, and there are also schists of these 

 complexes. 



The facts seem to warrant the following conclusions : — 



1. That all these rocks belong to one geological epoch ; that their 

 relations are principally those of segregation or separation, and in 

 a lesser degree of contemporaneous intrusion on the part of the less 

 basic and more acid portions of the magma. 



2. That the olivine portion of the magma now forming the 

 serpentine was the first to cool, followed by the others in the order 

 of their increasing acidity. 



3. That the serpentine is a non-intrusive rock, and one into which 

 all the other types of rock have been intruded, the granite intrusions 

 being the latest. 



IV. — On the Presence of Fossils in the "Azoic" Rocks op 

 Brittany. By M. Charles Barrois, Comptes Eendus des Seances 

 de I'Academie des Sciences, Vol. CXV. pp. 326-328, August 8th, 

 1892. 



ABED of quartzite containing crystalline scales of graphite is 

 intercalated in the gneiss of Morbihan. This gneiss passes 

 laterally into mica-schists by the disappearance of felspar. It 

 represents the azoic schists metamorphosed hy the injection of 

 "gi'anulite." The graphitic quartzite can be followed for a con- 

 siderable distance both to the north-east and south-west of the 

 Vanues-sheet of the Survey Map, into regions less affected by the 

 granulite. It is then found to be interstratified with mica-schists. 

 Si. Barrois has also determined the presence of the same band in 

 the north of Brittany, where the rocks are far less affected by the 



