JOHAN KL-ER. [SEC. ARCT. EXP. FRAM 



which tin- rapacniii> crt';itui-i' presumably could crush the cranial and 

 >n> plale> of the armoured lishes. 

 illi/f>fnlr/,is. which with HoloptychiuS forms appear to have 



common iu these region.-. was closely related in the above. The 

 latter were li-he- of a !> powerful hudd. with more -lender teeth and 

 round, thin scales of enamel. 



Finally, certain small Ostcolc-i>is forms appear also to have lived 

 there. They were powerful rapacious creatures, not exceeding ahoiit 

 20 30 cm. in length. 



The tithes which I have described confirm- the opinion which I ha\-- 

 already put forward, that the fossiliferous strata at Skrap Valley were 

 deported in a lar^e hrackish lake, possibly an estuary in which marine 

 and IVoli water lishes met. 



The tiny mussel. Pldonia, entered from the sea, adapted itself to 

 altered conditions of existence, and multiplied in liiii, r e quantities. Some 

 of the fishes, particularly the JIoloptyclnuN forms also indicate a free 

 connection with the >ea, for their remains are found hoth in purely 

 continental formation.-- (lake and river deposits) and in marine sediment-: 

 it is therefore natural to assume that like several forms of the present 

 lime. the-e creatures migrated from the sea to the rivers. This is also 

 indicated hy their wide extent over the whole of the northern hemisphere 

 in closelv related form-. 



. 



Other forms appearin:;. however, were presumahly genuine fre-h 

 water lishes, which like many of the recent forms were able to adapt 

 lliein-elve> to the life in brackish lakes. This feature concerns possibly 

 'i7///;/o/'7//.v. but e.-pecially ()xt<'oi<>i)ix. Psammosteus, and Bothriolepis. 



There is lm\\f\rr one point, that I desire to emphasise. It is not 

 pros I'd that a li.-hes ha> lived in a bracki>h water lake because \\eliud 

 iK remain^ in the sediment. The river or rivers that Mowed through 

 Midi a region may have carried the body with it and deposited it in a 

 different habitat. In >nch ca>e> there will always be a certain amount 

 of imcerlamlv. 



/ 



The olher fo--ilil'rron- hori/.ons that are to be found higher up in the 



series pre-enl a differrnl a-ped to that of the abundant lish hori/on o| 



Ski'ap X'alley. \oiie of them >how traces of marine nniels. and tin- 



li-be- of \\hich we lind remains are of Mich a character that we must 



inn- Ilii-m lo pure fre>h-\\ aler forms. 



In llx- dark -.-111-1- of < iali;eodden wilh remains of plants, which 

 appear lo be <pnl.- In.-al in appearance, we lind simply the small 

 /iV/,,-/Wr/,/.v and a -cale of <;li/i>/olri>is. At S. O. llaken there a-'e only 



