80 :E. A. Neu-ell Arber—The Ingleton Coal-field. 



constituents, with the addition of analcite; but the salic and femic 

 minerals are here more nearly on an equality, as in the typical 

 theralites. 



Theralites of a more normal type occur at Garlaff and Knockterra, 

 near Old Cumnock. In these there is approximate equality between 

 the amounts of the salic and femic constituents. The deep-purple 

 titanaiijjite builds large subhedral plates wliich ophitically enclose 

 small laths of felspar. There is no granulitic generation of augite. 

 Fresh olivine is fairly abundant. The nepheline is decomposed, but 

 may be recognized by its characteristic alteration. 



(b) Barshaw tjipe. — Mr. E. B. Bailey has described a theralitic 

 rock from a small sill at Barshaw House, near Paisley.' The chief 

 femic constituents are titanaugite and dark-brown soda-araphibole, 

 with sparse olivine and iron-ores. Labradorite and large allotrio- 

 morphic plates of nepheline form the remainder of the rock. The 

 nepheline is mostly decomposed to various secondary products, chlorite, 

 and analcite ; but the latter may also be primary. The rock is 

 decidedly melanocratic as may be gathered 'both from microscopic 

 study and the chemical analysis.^ The mineial constituents are the 

 same as those of lugarite, but analcite is more abundant in the latter, 

 which is undoubtedly the leucocratic facies of tlie Barshaw type. 

 This conclusion is supported by the fact that towards the top of the 

 Barshaw exposure occur contemporaneous bands and veins of lugarite; 

 but the nepheline in this rock is much fresher and more abundant 

 than in the type-occurrence of Lugar. The Barshaw exposure^ also 

 provides mesocratic types intermediate between theralite and lugarite. 

 With an increase in the salic constituents, especially analcite, goes 

 a significant increase in the idiomorphism of the titanaugite and 

 barkevicite, which culminates in the very perfect forms displayed by 

 these minerals in lugarite. 



A rock which probably belongs to the Barshaw type occurs in the 

 Inner Nebbock sill at Saltcoats, Ayrshire. Here, however, the 

 felspar and nepheline have entirely disappeared, and fresh titanaugite, 

 barkevicite, serpentinized olivine, and ilmenite are enclosed in a 

 groundmass of brilliantly polarizing zeolites. 



{To be conchided in the March Number.) 



V. — The Fossil Flora of the Ingleton Coal-fikld (Yorkshire). 



By E. A. Newell Arber, M.A., F.G.S., Trinity College, Cambridge, 

 University Demonstrator in Palseobotany. 



''pHE Upper Carboniferous rocks of the Ingleton Coal-field in 



1 JSTorth- West Yorkshire present a difficult study, and at the 



present time they are very imperfectly known.* As mapped by the 



^ Summary of Progress of Geological Survey for 1908, 1909, p. 44; also 

 Mem. Geol. Surv., The Geology of the Glasgoio District, 1911, p. 134. 



- Summary of Progress of Geological Survey for 1907, 1908, p. 55. This 

 rock is called " bekinkinite or theralite " by Bailey, Mem. Geol. Surv., Geology 

 of the Glasgow District, 1911, p. 134. 



^ Stimmary of Progress of Geological Survey for 1908, 1909, p. 44. 



■' J. E. Dakyns, etc., The Geology of the Country around Ingleborough 

 (Mem. Geol. Surv.), 1890. See also Davis & Lees, West Yorkshire (London, 

 1878), p. 167 



