Professor E. J. Garwood — Rock-building Organisms. 269 



Thougli the material so far to liand does not afford sufficient 

 evidence to warrant our assigning to it a definite systematic position, 

 there can be no doubt as to its importance as a rock-forming 

 organism. 



Genotype. — Aphralysia carbotiarta, sp. nov. (PI. XXT, Figs. 3, 4.) 

 The specimens so far met with appear to belong to only one species, 

 for which on account of its widespread occurrence in the Lower 

 Carboniferous rocks we suggest the specific name of ' carbonaria\ 



Horizons and Localities. — It occurs abundantly in the Lower 

 Carboniferous rocks of tlie North-West of England at the base of the 

 Seminula gregaria sub-zone. In the Shap and Kavenstonedale districts 

 of Westmorland ; also at the same horizon at Low Meathop in the 

 Arnside district ; more sparingly in the Solenopora sub-zone in 

 Stone Gill, Kavenstonedale ; in the upper Dihunophyllum sub-zone 

 {Girvanella Nodular Band) at Humphrey Head in the Grange 

 district; in association with Mitcheldeania gregaria in the Whitehead 

 Limestone at Mitcheldean ; at about the same horizon again in North 

 Cumberland and near Tosson in Northumberland ; also in the Modiola 

 beds underlying the Bryozoa bed in the Avon Gorge, Clifton, exposed 

 in the lower railway cutting near Cook's Folly. 



' Spongiostroma.' (PI. XXI, Fig. 1.) 



In 1906 Giirich described and figured a number of somewhat 

 obscure structures from the Dinantian rocks of the Naraur district 

 (under the generic names Spongiostroma, Malacostronia, etc.) which 

 he regarded as encrusting Foraminifera.^ Moi'e recently Professor 

 Kothpletz has described two species of Spongiostroma [S. balticum 

 and <S. Holnii) from the Silurian rocks of Gotland.- Giirich's 

 reference of these structures to the Protozoa appears to be decidedly 

 speculative, while the features which he selects for the subdivision of 

 the different forms into genera and species are very indefinite, and 

 the detailed structure often varies greatly, even in the same specimen. 



In the Lower Carboniferous rocks of Westmorland we meet with 

 many similar structures which in places contribute largely to the 

 formation of the deposit. They occur especially in the ' Algal Layer ' 

 at the base of the Seminula gregaria sub-zone, associated with Ortonella 

 and Aphralysia (PI. XXI, Figs. 3, 4), and occasionally form 

 undulating layers several inches in thickness. I have observed 

 similar structures in the rocks of North Cumberland and West 

 Northumberland and the Border countiy, also in the Forest of 

 Dean, the Avon Gorge, and South Wales,' and it is probable that 

 they will be found to be widely spread in shallow-water deposits of 

 Dinantian age in Europe. 



In transparent slices under low magnification they frequently 

 show a general appearance of stratification lying roughly parallel 

 to the bedding planes (PL XXI, Fig. 1), while fine layers of 

 a similar deposit are often seen under higher powers to be intergrown 



' Mevi. du Mus. Roy. d'Hist. Nat. de Belgique, t. iii. 



'•^ Kungl. Svenska Veicnskap. Hand., Bd. xliii, No. 5, 1908. 



* In specimens sent me by Mr. C. H. Cunnington. 



