Prof. Garwood — Calcareous Algce. 497 



Foreign Devonian. 



On the Continent the reported occurrences are, so far, equally- 

 poor. At the same time, the cursory examination which I was able 

 to make of the thin sections of the Devonian limestones exhibited in 

 the Brussels Museum leads me to expect that a careful investigation 

 of the Belgian Devonian limestones will yield other examples besides 

 Spongiostroma. 



Carbonifekotjs. 



We now reach, the period in Palaeozoic times when Calcareous Algae 

 attained their maximum development in England, a development 

 rivalling that which obtained in the Ordovician rocks of Scotland 

 and the Gotlandian of the Baltic area. The genera represented 

 include Girvanella, Solenopora, and Mif.cheldeania, while in addition to 

 these there occur several lime-secreting organisms which, though 

 still undescribed, will, I think, ultimately come to be included among 

 the Calcareous Algae. The most interesting of these organisms 

 I have recently figured from the Lower Carboniferous rocks of 

 Westmorland, where it forms a definite zonal horizon or 'band'.'^ 

 For this form, on account of its stratigraphical importance and for 

 facility of reference, I propose the generic name of Ortonella} 



Again, at the same horizon in the I^orth-West Province I have 

 .frequently noticed concretionary deposits of limestone which occur as 

 finely laminated masses, the laminae often lying parallel to the general 

 direction of the bedding planes, which on microscopic examination show 

 no definite or regular structure, but have every appearance of being of 

 organic origin. Many of these puzzling forms resemble very closely 

 the somewhat obscure structures found in the Visean limestones of 

 the Namur basin in Belgium, of which beautiful thin sections are 

 displayed in the Natural History Museum at Brussels,^ and which 

 Giirich has described and figured under various names — Spongiostroma, 

 Malacostroma, etc., and which he has included under a new family, 

 the Spongiostromidse,* and a new order, the SpongiostromaceEB. 

 I must confess that neither in the original sections nor in the 

 beautiful illustrations that accompany his work can I see any 

 grounds for referring these structures to the Protozoa. 



As regards the British specimens, I have long regarded them as 

 due, directly or indirectly, to the work of Calcareous Algae, partly on 

 account of their intimate association with well-developed examples 

 of these organisms and also on account of the entire absence of 

 Foraminifera and other detrital organisms wherever this structure 

 occurs. As, however, I have little doubt that they are closely 

 connected in their mode of origin with the Belgian specimens, 

 we may convenientlj^ speak of them under the general term 

 Spongiostroma. 



1 Q.J.G.S., vol. Ixviii, pi. Ixvii, fig. 2, 1912. 



^ Prom Orton, a village between Shap and Eavenstonedale, where this 

 organism occurs in great abundance. 



^ One of these is also exhibited at the Jermyn Street Museum. 

 ^ Mem. du Musee Eoy. d'Hist. Nat. de Belgique, tom. iii, 1906. 

 DECADE V. — VOL. X.— NO. XI. 32 



