548 Prof. Garwood — Calcareous Algoi. 



The diameter of the tubes is decidedly less than those iu Mitchel- 

 deajiia, being usually little more than half the size of the larger tubes 

 of J/! gregaria. The nodules of this genus occur in great profusion, 

 contributing largely to the formation of the shaly dolomite at the 

 base of the ' P. globosus band ' throughout the Shap, E.avenstonedale, 

 and Arnside districts in Westmorland and Lancashire. 



In addition to these genera there occur also two other encrusting 

 calcareous growths which require mention. The first of these 

 appears in thin sections in the form of a 'festoon-like' growth, 

 surrounding fragments of Calcareous Algse, especially Mitcheldeania 

 and Ortonella. I have met with it abundantly in the ' Algal band ' 

 in the north-west of England, but it also occurs not infrequently 

 associated with Mitch el dean i a iu the Whitehead Limestone in the 

 Forest of Dean, while a similar structure occurs associated with 

 Mitcheldeania gregaria in North Cumberland. 



The other deposit is the form already alluded to under the term 

 Sph(srocodmm, which I have found forming considerable masses of 

 rock in many districts where the Lower Carboniferous beds are 

 exposed, not only in Westmorland and North Cumberland, but also 

 in the Bristol district, the Forest of Dean, and South Wales. 



Foreign Carboniferous. 



From its general similarity to the British deposits we might expect 

 to find examples of an algal development in some portion of the 

 Belgian . Lower Carboniferous succession. As already mentioned, 

 large masses of encrusting calcareous deposits have been described 

 by Giirich ' from the Visean Limestones of the Namur Basin as 

 Spo7igiostroma, etc., which, though referred bj^ him to the llhizopoda, 

 may very well be calcareous precipitates deposited by algal influence. 

 Many of these deposits are similar to those mentioned above from 

 British rocks. 



No undoubted remains of Calcareous AlgDe have, however, yet been 

 recorded from these Belgian rocks. It may be of interest, therefore, 

 to mention the recent discovery by Professor Kaisin, of Louvain, of 

 certain algal remains in the beds overlying the Psammites-de- 

 Condroz at Feluy on the Samme. The form found here resembles 

 Ortonella of the Westmorland rocks, but the tubes are much finer, 

 and it may turn out to represent a species of Mitcheldeania. During 

 a recent visit to Belgium I had the pleasure of visiting the Comblain- 

 au-Pout Beds, in the Feluj' section with Professor Kaisin, and, 

 although these beds have been previously classed as Devonian, 

 I agree with him that they probably belong to the base of the 

 Carboniferous and correspond approximately to K of the Bristol 

 sequence. In the company of Professor Dorlodot and Dr. Salee, 

 I also visited the chief sections of the Visean, and we succeeded in 

 discovering at least three horizons at which nodular concretionary 

 structures, probably referable to algal growths, occurred. 



In 1908 Schubert (Jahrb. d. k. k. geol. Pudchsanstalt, 1908, Bd. 58, 

 Hft. 2, pp. 347, 382, pi. xvi, figs. 8-12) published descriptions of 

 two new forms of the Siphonese — Mizzia and Stvlleyella — from the 

 ' Mem. du Musee Eoy. d'Hist. Nat. de Belgique, t. iii, 1906. 



