KONGL. SV. VET. AKADEMIENS HANDL. BAND. 19. N:0 6. 9 



stone in eonsequence of its richness in reraains of Crinoidea, chiefly their stems and joints 

 of stems. But in addition to tliis, there are also other beds of limestone, which from 

 analogous reason have been denorainated corallian limestone. This, Iiowever, is only par- 

 tiallj^ true. With equal reason large portions of tlie limestone might be called Ox'thocera- 

 tite limestone or Bivalve limestone or Trimerella limestone or even Gastropodan limestone, 

 being then nothing else than a breccia of these shells. It is indeed sing-ular that the 

 remains of one group of animals should predominate över all others in several beds. 

 So for instance the fine grained limestone of Follingbo near Wisby consists largely of 

 shells of Cephalopoda and the same is the case with the rich quarries of Samsugn, 

 where Cephalopoda, somewhat mixed up with Gastropoda occur in enormous quanti- 

 ties. In other localities again shells of the Lamellibranchiates are the chief components 

 of the rock. The largest of all Silurian bivalves in Gotland, Megalomus gotlandicus 

 forms in thousands of specimens extensive banks, that stretch from the shores of Fårö- 

 sund in the north across the island to the immediate vicinity of Wisby and also along 

 the east coast at Ostergarn and along the shores south of that parish. The oolitic strata 

 near Bursvik contain almost only shells of Lamellibranchiates in great numbers of species 

 and specimens and a similar deposit of the same richness of identical forms occurs 

 further towards the north at Gothems hammar. At Bursvik and southwards to Hoburg 

 there lies along the coast a bank, half a foot thick, of Pterinea retroflexa and besides 

 several smaller. 



Then there are localities where the chief mäss consists of Brachiopoda, especially 

 of the genera Pentaraerus and Trimerella, the former within more circumscribed limits, 

 the latter as a true rockbuilder across the island in a belt from north east to south 

 west. The occurence of the Gastropoda is given below. At first I shall only enume- 

 rate the different localities, where they have been found, with some few remarks 

 concerning the geology and palteontology of their strata. 



Localities in the strattim a. 



Wisby. Shale beds north of that town and along the shore to Halls huk and 

 round that cliff a small distance south in the baj' of Kapellshamn, where they disap- 

 pear beneath the sea. 



Gnisvärd, a place south of Wisby to which the shale continues, rich in Brachio- 

 poda, partly common with Westergarn and partly with Wisby. A few Gastropoda 

 common with Wisby. 



Westergarn. Low shale beds, uncovered along the shore line, rich in fossils, 

 finely preserved. Pleurotomaria labrosa and bicincta are often found here. 



Stora Carlsö. The shale beds are well exposed along the east and west coast,- 

 chiefly rich in Corals and Brachiopoda. 



Djupvik in Fröjel and Eksta. There is a long stretch of the coast comprised under 

 this denomination from the northern shore of Skäret in Fröjel to the shore south of 

 Djupvik, being of almost the same soft, blue shale filled with a large number of fossils 



K. St. Vet.-Akad. Handl. Bd. 19. jS':o 6. 2 



