104 Annals of the South African Museum. 



lead to the conclusion that, if they be organic, they must have lived 

 on the spot where they occur as fossils. But as they are found in 

 deposits where they could have had no convenient support on which 

 to grow, the opinion to which he is driven is that S'piroijhyton and 

 allied forms are of mechanical origin and do not represent Algae or 

 other organisms. 



Potonie" reproduces a figure of Spiropliyton cifeliense originally 

 published by Kayser t from Lower Devonian rocks ; he states that 

 by stirring sand in water he w^as able to produce an appearance like 

 that of the typical Sjjirophyton. In an exhaustive memoir byFuchs]: 

 Spiropliyton and other problematical forms are discussed in detail ; 

 this author describes an Eocene specimen in the Pisa Museum 

 having a diameter of 40 cm. ; he deals also with Tertiary examples 

 from the Flysch and elsewhere. Eeference is also made to the well- 

 known screw-like fossils from America i; — the Devil's corkscrew or 

 Daimonelia, and Spiraxis, described by Newberry, Barbour, James, 

 and others ; Fuchs expresses the opinion that these various fossils 

 are all of similar nature and do not represent impressions of plants. 

 He suggests that Spirophyton and similar markings may owe their 

 origin to some animal, probably a worm, which produced a spiral 

 cavity in sand or other sediment, and another comparison he makes 

 is with the spawn-bands (" Laichbander ") of certain nudibranchs 

 {e.g., Doris). 



The examination of the Spirophyton specimens from South Africa 

 confirms my suspicion that this abundant " fossil " owes its origin to 

 mechanical causes. Spirophyton has so extended a geological range 

 that this fact alone makes one pause in describing it as a fossil alga ; 

 persistent types are well known to occur, but an organism with the 

 persistence of Spirophyton can only be recognised as such on con- 

 vincing evidence. The occurrence of this fossil in rocks, which are 

 in some instances almost destitute of undoubted organic remains, is 

 another fact to which some weight should be attached. But it is the 

 nature of the specimens themselves that furnishes the strongest 

 argument against the acceptance of Spiropliyton as an organism. 

 The strong and prominent ridges curving outward from a central 

 point do not convey the impression of records that are likely to have 

 been left by the thallus of an alga in a bed of sandstone ; the occur- 

 rence of the fossils in a vertical position traversing several inches of 

 a quartzose rock is a fact easier of explanation on the mechanical 

 theory of their origin. My view is that these Witteberg Spiro- 



* rotoni6 (99), p. 39. f Kayser (72). 



+ Fuchs (95), p. 410. S Newl)eiTy (8.')); James (95), &c. 



