( 503 ) 



11. Some years ago 1 made an excursion in Ihe suri-oundings of 

 Mnrmerwoiide in company with 'Sir. Hotkk, at the time a teacher 

 at Murmerwoude, now a teacher at a secojidary school at Nimegnen. 

 To the West of tliis viHage, situated in the north-eastern [)art of the 

 province of Frisia, ^ve found in the sand tiiat lay l)y the side of a 

 freshly-(hig canal two slal)-shai)ed [)ieces of sandstone thai tit each 

 other exactly and must have formed one whole. The dimensions of 

 the bigger i)iece are about 20, JO and 4,5 centimetres. The other 

 piece also possesses the two tirst-mentioned dimensions, but the third 

 is 3 centimetres. 



These pieces drew my attention as containing many more or less 

 complete stone-kernels and oiï-prints of pyramidal Hyolithus-shells. 

 The pointed ends of all these lie in the same direction, which must 

 certainly be attributed to the influence of streaming water. 



These erratic-blocks consist of hard, grey, very fme-grained sand- 

 stone. With muriatic acid ap[)lied to them there is no effervescence. 

 Here and there they show small, yellow-brown spots. Some of the 

 stone-kernels and that which lies close around them show the same 

 colour. 



The stone-kernels are straight and slowly increase in breadth. 

 The dorsal side is flat or somewhat concave; at the mouth it is more 

 or less convex. This side is not lengthened towards the front, so that 

 we have here a specimen of the subgenus Orthotheca. With the 

 exception of the dorsal side the surface of the stone-kernels is regu- 

 larly vaulted. Consequently the transverse section is about circle- 

 shaped, with only one segment cut off. Towards the pointed end 

 they become more or less triangular. In one stone-kernel, ^vhicil is 

 not exposed to view in its full length, the visible part points to a 

 length of about 35 millimetres and to a breadth, at the mouth, of 

 7 millimetres. 



It appears from these properties that these stone-kernels originate 

 from the Hyolithus (Ortliotheca)-species, whicli has been described and 

 pictured by Holm ^) as Hyolithus (Orthotheca) de Geeri. 



Holm tells us already that sandstone with Hyolithus de Geeri is 

 Under-Cambrian. I have, however, not been able to find in his work, 

 on what grounds this assertion is founded. Most problably lie came 

 to this conclusion because the nature of the stone points to it. At 

 the time sandstone with Hyolithus de Geeri ^vas not yet known as 

 firm rock. Even now I have not been able to find in the books at 

 my disposal, that saiidsloiic with llyolilhiis de Geeri should Ite known 



1) Holm. Sveriges Kambrisk-Siluriska Hyolithidao och Coiiiilariidac. Sveriges 

 geologiska Undersoknung. Ser. G. No. 112. p. 54. 



