152 Alfred Brammall — Intrusive Rock, 



Moreover, the fossils found at Barrow are on the whole the same, 

 and show a similar distribution, so that the bottom beds at Owthorpe- 

 and Barrow must be homotaxial. This being the case, it is evident 

 that the beds at Owthorpe can hardly be called " pre- Planorbis ", for 

 at the time of their deposition Planorbis was in existence a few 

 miles away. 



The character of the fauna in the lowest beds of all in the 

 Owthorpe district suggests a possible explanation of the absence of 

 Planorbis, for it is very impoverished, the only fossils being Modiola 

 minima and Ostracods (Cytheridea ellipsoidea, Jones). This type of 

 fauna is characteristic of lagoon phases, for, according to Mr. Dixon, 

 these are " all distinguished in places by exceedingly fine-grained 

 calcite mudstones with an impoverished fauna of Lamellibranchs 

 (especially Modiola), Ostracods, and Spirorbis. A certain amount of 

 terrigenous material, mud, and fine sand is found in them all". 1 



Confirmatory evidence of such conditions in the Owthorpe district 

 is seen in occasional worm bores and traces of ripple-marks. Further, 

 the occurrence of insect-remains at Barrow, indicating the proximity 

 of land, supports rather than opposes this view. 



"With regard to the underlying Bhaetic beds, it might be here 

 recorded that the top bed of Bhaetic limestone at Cotgrave Gorse is 

 cracked, the cracks being filled with calcite. The upper edges of the 

 blocks often show a pitted and bored appearance, which may in soma 

 cases have been caused by worms. A similar bed has been described 

 near Bath, and is there called the Sun Bed. 2 



I should like to express my thanks to numerous friends who at 

 various times have assisted me in the field, and to Professor H. H. 

 Swinnerton, of University College, Nottingham, whose inspiration 

 and help are mainly responsible for this little paper. 



IV. — The Intrusive Bock of Marston Jabet, Nuneaton, 

 Warwickshire. 



By Alfred Brammall, B.Sc. (Lond.), F.G.S., Assistant Director of 

 Education, Bury, Lanes. 



(PLATE VI.) 



1. Introduction and References to Literature. 



rPHE intrusive rocks of Marston Jabet and Chilvers Coton, though 

 JL probably of quite minor importance, have been rendered note- 

 worthy by the variety of opinions held regarding their true position 

 in a scheme of rock classification. This is especially the case as 

 regards the rock quarried at Marston Jabet. Thus Allport 3 comments 

 upon certain remarkable features distinguishing this rock, which, 

 however, seems to be covered by his general statement that the 

 intrusive rocks of the Warwickshire Coalfield are for the most part 

 ordinary diorites. Butley 4 concurs in the opinion expressed by 



1 Q.J.G.S., 1911, p. 571. 



2 Geology of Wellington and Chard (Mem. Geol. Surv.), pp. 27, 28. 



3 Q.J.G.S., vol. xxxv, p. 637, 1879. 



4 Geol. Mag., 1886, p. 562. 



