12 oG. LINDSTRÖM, A SILURIAN CYATHASPIS FROM GOTLAND. 
shell. These two circumstances, taken together with the fine 
and muddy nature of the shale beds, point to the conclusion, 
that there was a sheltered bay of the Silurian sea, where in 
the calm water with muddy bottom a fauna fourished rich 
in thin-shelled animals. The corals could not thrive well in 
a water so dissimilar to their usual abode, in the swell of 
the open ocean. : 
This fauna is in direct continuity and concordance with 
the faunas contained in the shale beds north and south of 
it, those at Östergarn and those of Grötlingbo in the south. 
Thus Phacops Downingie 1s a form typical for the strata 
of south Gotland, as well as Chirurus speciosus. Calymmene 
excavata occurs also in the limestone above the shale beds, 
and Calym. frontosa links them with the shale of Hablingbo . 
on the west coast of Gotland, Prcetus conspersus occurs as 
well in Östergarn as in Bursvik. 
The most characteristic fossils in the Lau strata are the 
two Conularie and the shields of the little Eumelozoé which 
in great numbers abound in the beds. 
Judging by the position of this shale under the hori- 
zontal limestone beds and by its continuity with the beds' 
all around it, it must belong to the age of the Wenlock shale 
or correspond to it, as the limestone beds nearest above it 
are of the Wenlock limestone age, and upwards pass into 
strata showing the character of the Ludlow beds. 
It was at first thought that these remains of fossil fishes 
were the oldest Silurian ones known in consequence of their 
occurence so low down in the series. CLAYPOLE, ') however, 
insists that he has found remains of fishes so low down as 
in the American Clinton group which according to him is 
coöval with the English Upper Llandovery. When I wrote 
the preliminary note of the discovery of these Gotland fos- 
sils. ?) I was not aware of his paper, nor of a memoir by 
Dr RoHoNn, 3?) in which he describes some fossil fish teeth from 
a still lower level, the Lower Silurian strata called the 
Glauconite sand near S:t Petersburg in Russia. 
Besides this Cyathaspis? Schmidtii there have been found 
in the shale beds of the same age, but some miles further 
') Qu. Journal Geol. Soc. 1885 p. 56, and also >Nature»> vol. 52, 1895, p. 55. 
?) Geol. Magazine 1895, p. 170. 
3) Ueber uvtersilurische Fische 1889. 
