Linnarsson — On the Eophyton Sandstone. 397 



■weathering of the felspar, and by no means, as the true arkose, a 

 sandstone-like rock. In visiting the millstone quarries of Lugnas last 

 autumn, I felt convinced, almost at the first glance, of the truth of Dr. 

 Wallin's determination. The mica scales are often seen to be arranged 

 in well-marked laminas, usually dipping almost vertically, so as to 

 produce a more or less distinct gneissose structure. Besides this the 

 rock (as stated by Dr. Wallin) increases in hardness downwards and 

 resembles more and more the unchanged gneiss of the neighbour- 

 hood. 



Thus it is above the millstone bed, that the oldest Cambrian de- 

 posit commences. The all but horizontal sandstone overlies un- 

 conformably the nearly vertical strata of the millstone gneiss. In 

 the quarries its lower division only is exposed. The rock nearest to 

 the gneiss is, as before mentioned, a conglomerate, the sandstone-like 

 cement of which contains larger or smaller rounded fragments of 

 quartz and grains of felspar, the latter sometimes being, as in the 

 millstone gneiss, converted into kaolin powder. In the fourth 

 volume of his "Anteckningar"^ Hisinger has given a tolerably 

 accurate description of this conglomerate, but he says afterwards, 

 erroneously, that the millstone bed is in immediate contact with a 

 fine-grained sandstone.^ The conglomerate is usually concreted into 

 one mass with the millstone gneiss, but the limit, as may be 

 expected from the different nature of the rocks, and above all, from 

 their unconformable stratification, is very distinct. As yet no fossils 

 have been found in it. 



The thin conglomerate is followed, often without any very distinct 

 line of demarcation, by the main mass of the lower sandstone, which 

 is fine-grained, hard, greyish, and reddens in the air. Except in its 

 undermost parts, its layers are very thin. It is interbedded with 

 thin layers of a greenish-grey shale. Sometimes the sandstone, 

 owing to a greater number of laminae of mica, assumes a schistose 

 structure. Hisinger and Sir E. Murchison have already described 

 this sandstone and the shale alternating with it ("bluish-grey clay" 

 Hisinger, "greenish-grey shale" Murchison). Dr. Wallin has not 

 only pointed out all its petrographic characters, but also remarked 

 that it contains pecixliar fossils, and for that reason, oi] the sug- 

 gestion of Professor Torell, he has termed it "Eophyton sandstone," 

 reserving the name of Fucoid sandstone for the upper and softer 

 parts. It is especially in the deep and numerous quarries on the 

 north-eastern side of the mountain that sections of the Eophyton 

 sandstone are exposed, but the limit next the Fucoid sandstone 

 proper is not exposed there and has not been observed in any other 

 place. The thickness therefore has not been ascertained. Dr. Wallin 

 has found it to be at least 30 feet. 



It was in this sandstone that Dr. Wallin during the summer 1867 

 discovered the Eopliyton Linnaanum, Torell, and in the following year 

 he added the Arenicolites spiralis, Torell. Last autumn I visited 

 Lugnas, and collected the fossils I am about to describe. The 

 rock, being very fine-grained, has preserved distinct casts of the 

 1 P. 49. 2 Yol. v., p. 67 ; Vol. vi., p. 60. 



