256 A. B. Hunt — Granitoid Fragments in Culm. 



Nautilus expansus, J. de C. Sowerby. 



,, Largilliertianus, A. d'Orbigny. 

 Acanthoceras hippocastanum (J. de C. Sowerby). 



,, ,, ,, , var. co?wpjvssa, Jukes-Browne. 



„ Mantelli (J. Sowerby). 



,, naviculare (Mantell). 



Schloenhachia Goupiliana (A. d'Orbigny). 



,, varians (J. Sowerby). 



Placenticeras Largilliertianum (A. d'Orbigny). 

 Scaphites eequalis, J. Sowerby. 



>) )) )) '^"^i"- 



Baculites, sp. 



IV. — Notes on certain Granitoid Fragments from the Culm 



CONGLOMEBATES, AND ToURMALINIZED GrITS FROM THE NeW 



Eed Conglomerates of South Devon. 



By Arthur E.. Hnut, Esq. 



WHEN studying the Dartmoor Eocks some years ago I was 

 anxious to ascertain wlietlier any fragments referable to 

 Dartmoor could be detected in the Culm conglomerates and Culm 

 sandstones of South Devon. Sections cut from these rocks, collected 

 for me by my friend Mr. W. A. E. Ussher, F.G.S., proved in every 

 way BO dissimilar from Dartmoor rocks and minerals that further 

 investigation in that direction appeared useless. About the same 

 time I collected a variety of fragments from the New Bed breccia 

 at Labrador, near Teignmouth, while Mr. Ussher supplied me from 

 other localities. These, again, even when schorlaceous, differed 

 so much from any rocks known to me that I postponed further 

 inquiry in that direction also sine die. The facts seemed important, 

 but the clue to their interpretation was wanting. During the past 

 year Messrs. A. Somervail and Harford Lowe, Hon. Secretary and 

 Hon. Treasurer of the Torquay Natural History Society, have been 

 fortunate enough to obtain a number of specimens of a very fine- 

 grained granitic rock among the pebbles of the Culm conglomerate 

 in the neighbourhood of Eoydon, South Devon.^ These interesting 

 rocks they have been good enough to submit to me for examination, 

 with a view to ascertaining how they compare with the well-known 

 types of the Dartmoor granites. Mr. Teall has also kindly lent me 

 a slide cut from one of Mr. Somervail's specimens in his possession. 

 I have seen altogether six slices of different specimens of the Culm 

 conglomerate granites. 



My knowledge of petrology does not warrant a technical descrip- 

 tion of the slides with identification of the felspars, so such will not 

 be attempted. The six slides, though slightly differing, present 

 a very strong family likeness and are all very fine in grain. One or 

 other of them presents the following marked distinctions from any 

 ordinary type of Dartmoor rocks known to me : — 



(1) A tendency to a parallel arrangement of quartz and mica. 



(2) Micro-porphyritic microcline and plagioclase, in a finer matrix. 



(3) Felspars, occasionally bent. 



1 See A. Somervail, Geol. Mag., Dec. IV, Vol. V, p. 509. 



