16 PROF. E. J. GARWOOD AND MISS E. GOODYEAR [vol. Ixxiv, 



We tabulate here two chemical analyses of the rock : — 



New Dolyhir Quarry. Yat Hill Quarey. 



Per cent. Per cent. 



Calcium carbonate .. > 99'46 99*11 



Magnesium carbonate trace trace 



Ferrous oxide and alumina do. do. 



Silica 0-20 0-10 



Phosphoric acid trace trace 



Sulplrarie acid do. do. 



Totals 99-66 99-21 



Fauna and flora. — The fauna consists chiefly of bryozoa, 

 corals, and brachiopods, crinoid- remains being inconspicuous (except 

 in the basement conglomerate). Good specimens can only be 

 extracted from certain portions of the deposit, as the rock has been 

 subjected to a considerable amount of solution and recrvstallization. 

 The most interesting feature of the deposit, however, is the presence 

 of abundant remains of calcareous alga?, especially Solenojpora, 

 which, in places, constitutes fully half of the rock. This organism 

 occurs in the form of irregular nodular growths, varying in size 

 from that of a pea up to masses 17 centimetres in diameter. In 

 the freshly quarried portions of the rock these nodules are of a deep 

 purple colour, and might easily be overlooked ; but, after exposure, 

 they gradually lose their colour, and appear on weathered surfaces 

 as conspicuous white spots, scattered through the deposit. The 

 typical porcellanous structure so characteristic of this organism is 

 well seen on freshly fractured surfaces, and differentiates it from 

 the surrounding coarsely crystalline rock. 



Callaway appears to have noticed portions of Soleuopora in his 

 thin sections, but evidently considered the structure to be inorganic, 

 for he remarks : ' 



' Some of it displays a compound polygonal structure, suggesting a Favosites. 

 I think, however, that this is only mimicry, and that it is really concretionary, 

 consisting of aggregations of tubular bodies. That it is not organic appears 

 from its relation to the fossils.' * 



Good specimens may be seen in the local buildings, as, for example, 

 at the railway station and at Yat Farm ; and a xery fine slab of 

 this alsral limestone has been erected in Old Radnor Churchyard, 

 in memory of the late Sir Edmund Herbert Frankland Lewis. 2 A 

 fine example of the rock is preserved in the geological museum at 

 University College, Gower Street. 



1 Q.J. G. S. vol. lvi (1900) p. 517. 



2 A descendant of Sir T. Frankland Lewis, who, as stated by Murchison, 

 with his son Mr. George Lewis, ' first urged me to put together all my geo- 

 logical documents respecting this region,' and thus form the work afterwards 

 called ' The Silurian System." See ' Siluria ' 1st ed. (1854) p. 104. 



