Pengelly — Devonian Rocks of Torhay. 19 



ABSTEACTS OF BEITISH AND FOEEIGN MEMOIES. 



I. — Ammonites from the Himalayas, etc. 

 (PALiEONTOLOGiscHE MiTTHEiLUNGEN. Nos. IV. and V. von Prof. Dr. A. Oppel.) 



IN this, his third contribution to Paleontology, Dr. Oppel first 

 concludes his descriptions and figures of the Ammonites which 

 are contained in the Schlagintweit collection of fossils from the 

 Secondary formations of the Himalayas, and the discussion of which 

 was commenced in the second part of the " Mittheilungen." The 

 formations represented by these fossils appear to be equivalents of 

 the Kelloway rock, Oxford Clay, and Hallstadt beds of Europe ; but 

 the author .makes some cautious reservations on account of considera- 

 tions founded on the inferred existence of " Homoiozoic belts" during 

 the Jurassic period. 



The succeeding memoir is devoted to a G-eological Study of the 

 Department Ardeche, in which the author recognises the Oxford 

 Clay, Kelloway rock, and part of the Bath Oolite. Dr. Oppel 

 describes the strata in the neighbourhood of Yalence, and gives a 

 section and copious lists of fossils, showing the stratigraphical and 

 palgeontological relations of the different beds, which he considers to 

 represent the following zones of life : — 



Zone of Terehratida impressa, \ 



,, Ammonites transver sarins \ r\ c j p-i 

 5, Ammonites cordatus i ■^' 



„ Ammonites Lamherti ] 



„ Ammonites atlileta \ 



,, Ammonites anceps > Kelloway rock. 



„ Ammonites macrocephalus ] 



Bath group. H. M. J. 



II. — On Cektain Joints and Dikes in the Devonian Limestones 

 ON THE Southern Shoke of Torbay. 

 By Wm. Pengelly, F.R.S., F.G.S., etc. 

 [Read before the Members of the Torquay Natural History Society, Nov. 8, 1865.] 



MOST rocks are traversed by various kinds of divisional planes, 

 some being coeval with the rocks themselves, whilst others 

 have certainly been superinduced. 



In stratified rocks the principal planes of division are those of 

 stratification, lamination, foliation, cleavage, and jointage. 



Stratification and lamination differ in degree only. Each marks 

 a pause — greater or less — in the process of deposition or sedimenta- 

 tion. Foliation is chiefly confined to crystalline strata, and is 

 applied to rocks composed of laminge alternately of different kinds of 

 mineral matter. The planes of lamination may or may not be 

 inclined to those of stratification. 



Cleavage is that tendency which occui's in many rocks — but 



