C30 Geological Society. 



Part II. — Notes on the Ammonites. 15v Leonard Frank Spath, 

 D.Sc, F.G.S. 



The paheontologieal ])art contains de.'^eriptions of the genera of 

 ammonites found in the Shales-witli-lJeef, and remarks on their 

 classitieation and i)hvlogeny. The following new genera are 

 proposed: — Paraniioccras ; genotype, tlie species to which spe- 

 cimen No. 2713, Coll. W. D. L., helongs, identified hy the Author 

 with Ammonites alcinoe Keynes (lS7i>, pi. xxiii, fig. 10). 



Siilcifcrites ; genotype, the species to which specimen IJrit. 

 Mus. C. 104:10 helongs, identilied hv the Author as Ammonites 

 sttlcatus J. Buckman (Pal. Univ. 1904, No. 39, Hg. 2). 



Part III.— IVtrological Notes. Bv William Alfred Richardson, 



M.Sc, F.G.S. 



The development, in some beds, of lamination by weathering is 



described, and the presence of barytes recorded. A study of the 



concretions leads to the following conclusions as to the sedimentary 



history of the beds : — 



(1) During sedimentation, calcium carbonate gradually accu- 

 mulated in solution in the watei'logged deposit. 



(2) During the initial stiiges of desiccation and draining, a 

 system of limestones and calcareous nodules was precipitated 

 rhythmically. 



(3) During the later stages of desiccation, veins of fibrous 

 calcite were deposited at levels of low pressure. Cone-in-cone 

 structure, found in these veins, is due to pressure operating during 

 growth, partly by spreading the growing crystals and jiartly by 

 setting up planes of shearing closely parallel to the cleavage of 

 the fibres. 



(4) The remaining solutions of calcium carbonate were ulti- 

 mately deposited as a cementing material, on the final di'ying of 

 the deposit. 



January 18th, 1922.— Mr. R. D. Oldham, F.R.S., 

 President, iii the Chair. 



The following communications were read : — 



1. ' Jurassic Plants from Ceylon.' By Prof. Albert Charles 

 Seward, Sc.D., F.R.S., F.G.S., and R. E. Holttum, B.A. 



The collection of plant-imjn-essions described b}' the Authors 

 was obtained by Mr. E. J. Wayland, from a shale resting ujwn 

 Arch;uan rocks at Tabbowa in the North-Western Province of 

 Ceylon. These are the first fossil plants recorded from that island. 

 Of the six species determined five ajipear to bo identical with 

 plants described by Feistmantel from Jurassic rocks on the 

 Madras coast; these are : — 



CladopJilebis reversa (Feistmantel) ; C. dcnticiihila (Bron- 



gniai-t). 

 Tceniopteris spatiilota fMcClellan). 

 Arducfirifcs citfchensis (P'cistmanh'l). 



