Reviews — Geology of the South Wales Coalfield. 171 



Miss Elles, Sc.D., has kindly furnished the following preliminary- 

 list of fossils from the deposits : — 



Orthoceras sp. Strophomena antiauata (Sad.). 



Dalmanella (Orthis) elegantula Zygospira sp. 



(Dalm.). Murchisonia cf. torquata (McCoy). 



Skenidhwi Lewisii (Dav.). Holopella cf. tenuicincta (McCoy). 



Ccelosplra (Atrypa) hemispherica Cyclonema sp. 



(Sad.). Comulites. 



Caviar otcecliia (Rhynchonella) Monticulipora fibrosa (McCoy). 



nucula (Sad.). Crinoids, Bryozoans, and Corals, 



Dayia (Rhynchonella) cf. navicula and perhaps Trilobites, but 



(Sad.). nothing identifiable. 



IFLIE^riE-'^S. 



I. — Memoirs op the Geological Survey 

 The Geology of the South Wales Coalfield. Part XI : The 



COUNTRY AROUND HAVERFORDWEST, BEING AN ACCOUNT OF THE 

 REGION COMPRISED IN SHEET 228 OF THE MAP. By AUBREY 



Strahan, Sc.D., F.R.S., F.G.S., T. C. Cantrill, B.Sc, F.G.S., 



E. E. L. Dixon, B.Sc, F.G.S., H. H. Thomas, M.A., B.Sc, F.G.S., 



andO. T.Jones, D.Sc,F.G.S. pp. i-vii, 1-262. 1914. Price 3s. 6d. 



fPHE memoir before us deserves a somewhat extended notice, for 



1 much of its contents is of more than local interest. Were we 



to start our classification of the Lower Palaeozoic rocks afresh, we 



should probably adopt this area as the type-area of the rocks of 



Ordovician age, and the lower division of the Silurian strata is also 



remarkably well represented. It is safe to say that students of the 



Ordovician and Lower Silurian strata will in future turn again and 



again to the pages of the memoir. The map of which the memoir is 



descriptive has not yet been published. 



The district includes rocks of Pre-Cambrian, Cambrian, Ordovician, 

 Silurian, Old Red Sandstone, Carboniferous, and Eocene (?) ages, and 

 also Glacial and Post-Glacial accumulations. 



The oldest rocks occur in two masses south of the coal-field, the 

 southerly being termed the Benton Series (which also appears in 

 a smaller patch further south) and the northerly the Johnston Series. 

 The rocks of the former consist of acid lava-flows with tuffs and 

 agglomerates which are probably of more basic character. The 

 Johnston Series is one of plutonic rocks consisting (in the order of 

 their intrusion) of quartz-diorites, quartz-albite rocks, and quartz- 

 dolerites. The two series adjoin for about a mile, but the nature of 

 the junction is unknown. The Rosemarket Rocks (of Valentian age) 

 probably rest unconformably on the Benton Series, and the Johnston 

 Rocks are also presumably older than the Rosemarket group. There 

 are reasons for supposing that these Johnston Rocks are Pre-Cambrian, 

 and it is likely that the Benton Series also should be referred to that 

 age. Cambrian rocks of Lower Lingula Flag age are exposed on the 

 •east of the Western Cleddau at Spittal Cross and Trefgarn Bridge, and 

 •on the west of that river near Leweston and Wolfsdale. 



The development of the Ordovician strata, notwithstanding certain 

 breaks, is very complete, and the small thickness of intercalated 



