Correspondence — G. Dewalque F. A. Bather. VI. 134 



THE HORIZON OF BINOCYSTIS BARROISI. 1 



[Geol. Mag., n.s., Dec. IV, Vol. VI, pp. 134-136 ; March, 1899.] 



Sir, — Professor G-. Dewalque, writing in your February number 

 (n.s., Dec. IV, Vol. VI, p. 94), gently turns the Famennian beds of 

 the Condroz right way up again from the reversed position into 

 which an annoying slip on p. 543 of my paper had thrown them. 

 For this friendly intervention he has my thanks, but with his main 

 thesis I am unable to agree. The question at issue is the horizon of 

 Dinocystis Barroisi ; to this all the rest is subsidiary. Let us make 

 the question clear by printing the list of the horizons of the 

 Famennian, in descending order, as given in " Legende de la Carte 

 Geologique de Belgique, etc.," 8vo, Bruxelles, 1896. 



Devonien superieur. 



Famennien superieur. 



Assise de Comblain-au-Pont [=Etroeungt Limestone]. 

 Assise d'Evieux. 

 Assise de Monfort. 

 Assise de Souverain-Pre. 



Famennien infer ieur. 



Assise d'Esneux. 

 Assise de Mariembourg. 

 Assise de Senzeilles. 



This list does not imply an absolute vertical succession : it appears, 

 for instance, that the Assise d'Evieux, with its rich flora, may be 

 a more littoral facies of the Assise de Monfort, while the Assise 



1 See Geol. Mag., n.s., Dec IV, Vol. V, pp. 543-8 (December, 1898). Footnote 1 

 on p. 547 explained the name Dinocystis as derived from deivSs, terrible. Although 

 this seemed peculiar, it did not occur to me that Dr. Jaekel must have intended to 

 derive it from Siuelu, to whirl round, in allusion, to the marked curvature of the radial 

 grooves. Thus regarded, the name is highly appropriate. 



