4 G. LINDSTRÖM, THE ASCOCERATIDAE AND THE LITUITIDE. 
Ä. Cephalopodan: Stratä:—3:-5-2-5-s13 T3K40955 0 SCENER Ne ] 
g. Megalomus banks, also with: Trimerella == 0 | 
f. Crinoidal and coralline conglomerate: Beds.mosoooso p Ludlow beds 190 feet 
e. Pterygotus and Palxophonus beds, chiefly near Wisby, but 
also -Ocenurring. in Other plagest= 5.55 soo Aer sea erna | 
d. Wenlock limestone, in the north of Gotland bands of shale 
and limestone, the latter increasing upwards. In the south 
of the island, above the sandstone, there are oolite beds 
alternating with limestone, both containing bivalve shells 
in great MUNber..t bss os se sn AE ST I AE Tre 40 feet 
ce.  Shale beds with Orthis Lovéni, Strophom. Lovéni, Stroph. 
Walmstedti near Wisby. Faunal character changing towards 
south; distinct, but coöval faunal regions formed at Wester-It .., 
i Wenlock shale 80 feet 
garn — Stora Carlsö, Fröjel, Eksta, Hablingbo. The litho-/ 
logical character by degrees changed into sandstone from 
Rohne GrötlingboitorHoburgtad alder stt oss 
b. Marly beds most developed north of Wisby near the level of 
the sea. Stricklandinia lirata, Bronteus platyactin, Palxo- 
cyclus porpita, Goniophyllum pyramidale, Leperditia baltica,! 
Calymmene papillata 
Upper Llandovery. 
a. Red shale, below the level of the Baltic. It has fossils in common with b and c, as 
Goniophyllum, but of a peculiar type, Phacops quadrilineata. Arachnophyllum typus 
is the most characteristic; there are also some peculiar brachiopoda. 
It is highly probable that the uppermost, vast deposit of the Cephalopoda (h) was 
formed in shallow water near the shores. The immense masses of the shells of these ani- 
mals, which in some places almost entirely make up strata from four or five feet in thick- 
ness from the smallest to the most gigantic specimens, prove the litoral character of the 
deposit. After the death of the animal and the decomposition of its soft parts the shell 
must have been floating on the surface of the sea, buoyed up by its manifold air cham- 
bers, unless they were replenished with organic deposits. Having drifted about, they 
were washed ashore in large numbers, quite as Spirula now a days, which in innumerable 
heaps covers the shores of the ocean islands. 
In these localities of the uppermost limestone the Silurian Cephalopoda lie inbedded 
almost péle-måéle, species of many genera, often exclusively such, but sometimes with small 
gastropoda, bivalves, brachiopoda and corals mixed up with them. Generally the Ortho- 
ceratites lie horizontally, but also in all other imaginable positions. 'The immense lapse 
of time during which the deposition of these strata lasted, may be inferred from the follow- 
ing facts. There is namely good evidence that a great number of the Orthoceratites had 
been fossilized, nearly as we now see them, already in the Silurian sea, before they were 
entombed in the sediment forming on its bottom. The Orthoceratites are very often, 
especially in certain localities, as for instance in Östergarn, found deprived of the shell, only 
as nuclei and the chambers filled with mud, hardened into stone, or with calcareous spar. 
On the surface of this nucleus other smaller Upper Silurian organisms, as Corals and 
