226 Revieics — Dr. Bornemann — Cambrian Fossils of Sardinia. 



serpentine without trace of fibrous structure is produced. The next 

 stage is a general hydration of the whole ground-mass, the disap- 

 pearance of alumina from its composition, and the oxidation of 

 magnetite into peroxide of iron. 



Such changes are analogous to those observed by Prof. Heddle in 

 the serpentinous marbles of Tyree, Lewis, and other places in the 

 North of Scotland, where augite has been converted into serpentine ; 

 as well as in the picrolite of Balta and the crysotile of Fetlar, where 

 forms of hornblende have been so changed ; it is very similar to that 

 which he observed at Beauty Hill near Aberdeen, ■ where waxy 

 lahradorite (a mineral closely resembling the felspathic component 

 of the Porthalla stone) " is seen to pass within a space of about an 

 inch into this mineral " (an aluminous serpentine or pseudophite) 

 '■' by insensible gradation." The italics are all the Professor's. For 

 the full discussion of the processes of change in these different 

 circumstances, which to me is perfectly conclusive, I must refer to 

 the original paper in the Proceedings of the Eoyal Society of 

 Edinburgh. On the whole, it seems to me that serpentinous change 

 in hornblendic and augitic substances is little less common than the 

 kaolinization of felspar ; and these two modes of metamorphism are 

 not unfrequently to be seen in the same rock-mass, as at Duporth 

 (see Min. Mag. vol. i.), Cant Hill (see supra), and many other places. 



E, IB "V IIB AAT S. 



1. — Die Veksteinekttngen des Cambrischen Schiohtensystems 

 DER Insel Sakdinien, nebst vergleichenden Untersughungen 



■iJBER ANALOGE VoRKOMMNISSE AUS ANDERN LaNDERN. VoU Dr. 



J. Georg Bornemann, M.A.N. Erste Abtheilung. Mit 33 Tafeln, 

 No. i. — xxxiii. Nova Acta der Ksl. Leop. -Carol. Deutschen 

 Akademie der Naturforscher. Band LI. No. 1. (Halle, 1886.) 

 The Eossils of the Cambrian Strata of the Island of 

 Sardinia, with a Comparative Study of similar for3is from 

 OTHER Countries. By Dr. J. Gr. Bornemann. 1st part, 4to. pp. 

 83, and 33 plates. 



THE present is the first portion of a work in which the author 

 proposes to give a complete description of the fossils from the 

 Cambrian strata of Sardinia, which he has collected during succes- 

 sive visits to the island. Owing to the extremely complex manner 

 in which the strata have been disturbed, it has not been possible to 

 make out in detail the succession of the beds ; but the oldest fossil- 

 iferous rocks near Canalgrande on the west coast of the island, con- 

 sist of a series of clay-schists, rich in Trilobites, quartzitic sandstones 

 with sponge (?) remains, and dark crystalline, and in part oolitic, 

 limestones. These are succeeded by a great thickness of massive 

 limestones, followed by successive alternations of shales with Lingula, 

 sandstones with Trilobites, and limestones containing large numbers 

 of the peculiar Coral-like fossils known generally as Archceocyathus. 

 Associated with these Coral (?) bearing limestones and marbles are 

 coarse sandstones filled with Cruziana. 



