106 Annals of the South African Museum. 



from which irregular ridges and grooves extend in double curves over 

 the face of the rock, forming a figure reminding one of the lines of 

 sparks given off from a rotating Catherine "Wheel ; surface features 

 more obscure than in the figured specimens. The depth of the 

 grooves and the prominence of the ridges are in themselves a^ 

 weighty argument against the view that we have before us the 

 impression of an algal thallus. 



3. From Worcester; a small specimen similar to that shown in 

 fig. 2 ; 403. 



