Vol. 54.] FAUNA OF THE 8KIDDAW SLATES. 525 



IV. Comparison of the Skidd aw Slate Fattna with similar 

 Eaunas in Sweden and Canada. 



The appended table (II, pp. 526-527) shows the relationship of 

 the Skiddaw Slate fauna to that of other areas. It will be observed 

 that, though it is more closely related to the fauna of the Quebec 

 Group of Canada than to that of any English beds, it is still more 

 nearly related to the Swedish fauna ; for, while of the whole 

 59 species, 25 are common to the Skiddaw Slates and the Quebec 

 Group, and only 14 common to the Skiddaw Slates and the two 

 other English areas, no less than 34 species are common to the 

 beds of Sweden and the Skiddaw Slates. 



Of the total number found in the Skiddaw Slates, 15 species are 

 peculiar to the beds, 4 occur elsewhere only in Canada, and 17 in 

 Sweden only, while but one is confined to other English areas. 



In the table those species marked (a) are also present in the 

 Arenig beds of Australia : those in the Swedish column marked (5) 

 occur in beds below the Phyllograj^his-skiffeT ; those marked (c), in 

 the PhyJlograptus-^\i^eT and higher beds ; and those marked {d), 

 exclusively in higher beds. 



It is also worthy of note that those marked (c) occur in the 

 Phyllograptus-skif^er, only in the zone of Pliyllograptus of. typus, 

 Hall, which oveilies the (9r^7iocer«s-limestone, and is therefore at 

 the very top of the Phyllograptus-heds. 



Bryograptus Callavei, Lapw., occurs in the Shineton Shales of 

 England. 



V. General Conclusions. 

 (a) Stratigraphical. 



The fauna of the Skiddaw Slates points to the beds being in the 

 main of Arenig age, but it also indicates beds belonging to a lower 

 and to a higher horizon. 



The occurrence of Bryograptus and Clonograptus teneUus points 

 to the existence of beds of Tremadoc age, and though evidence has 

 not yet been brought forward to show the existence of still older 

 rocks, their occurrence is not unlikely. It has been shown that the 

 beds have near equivalents in Sweden and Canada. The Tremadoc 

 Beds above mentioned undoubtedly correspond with the shales 

 containing Bryograptus, which in some Swedish districts (Scania, 

 etc.) take the place of part of the Cer atopy ge-Vdlk. 



In most Swedish localities Graptolite-shales succeed the Cera- 

 tojoyge-kaXk, and these are overlain by the Orthocerkalk (OrtJioceras- 

 limestone), which represents everything up to the zone of Cceno- 

 graptus gracilis. In Scania, however, the succession is rather 

 different; the Orthoceras-limestone is not nearly so thick; Tullbero- 

 separates off a bed of shales lying immediately above it, as the zone 

 of PhylJograptus cf. typus, Hall, and this forms the highest bed 



