228 Mr. H. B. Brady on a 



Affinities. — The Nummulina antiquior of Rouillier and Vo- 

 sinsky, judging from the figures accompanying their memoir^ 

 is essentially unsymmetncal. Not only are the two faces very 

 unequal in their convexity, but there seems also a tendency 

 to irregularity in the contour of the periphery. The Orobias 

 cequalis of D'Eichwald much more nearly resembles the speci- 

 mens before us in external characters. Its separation by the 

 author from the genus Nummulina^ on the ground of the 

 minute stracture of the shell (resting, as it apparently does, on 

 negative data), need not be insisted upon. The absence of 

 evidence of tubulation or canals may be dependent upon the 

 process of mineralization ; and their detection in fossils so 

 minute, taken from a compact calcareous rock of such an age, 

 must always be attended with difficulty. Nevertheless some 

 doubt must rest upon this species until further specimens 

 from the same locality, or at least from a similar horizon, have 

 been minutely examined ; and as it differs materially in size * 

 and septation from the organism just described, it appears 

 undesirable to associate them under the same specific name. 

 I propose therefore for the Belgian specimens the name Num- 

 mulina jy^'istina. 



Referring toD'Archiac and Haime's monograph f? the figures 

 most closely resembling the new N. prisfyina are those of 

 N. variolaria^ Sowerby, which represent a Nummulite of 

 somewhat larger dimensions but remarkably similar in general 

 external characters and septation. Thus the nearest allies, 

 zoologically speaking, of the Carboniferous form are the 

 small thick members of the " radiate " group regarded by 

 Messrs. Parker and Jones as the western modifications of 

 N.pJanulataX. N. variolaria especially is a poor and variable 

 form whose descent may be easily traced. 



It is not a little singular that in the Carboniferous precursor 

 of the Nummulitic group we should have an organism so 

 exactly corresponding in minu.test features with its most 

 modern representatives. This cannot be a mere coincidence. 

 Is it not rather a curious exemplification of persistence of 

 essential characters through innumerable ages, whilst modifi- 

 cations of the original, forming collateral '' species," have, 

 under favourable circumstances, exhibited an extraordinary 

 development in size and complexity of structure and a cor- 

 responding increase in geological importance? Then, as ex- 

 ternal conditions have become less favourable, little by little, 



* Tbe diameter, as given by D'Eichwald, is five times as great as the 

 largest of the Belgian specimens. 



t Descr. des Auim. foss. du groupe Nummulitique de I'lnde, p. 14G, 

 pi. ix. fig. 13, a-g. 



X See Messrs. Parker and Jones on the nomenclature of the genus, 

 Ann. & Mag. Nat. Hist. 3 ser. vol. viii. p. 231. 



