part 4] 



JUEASSIC CHEONOLOGY. 



439 



lower portion of the ' marlstone ' is a harder and much coarser 

 rock, and is often highly conglomeratic. Most of the pebhles are 

 made up of a similar coarse ' marlstone ' ; but pieces of a compact 

 blue limestone and micaceous sandstone occur. Many large flat 

 pebbles are thickly encrusted with a small Serpula and riddled by 

 LitJiopJiar/us horiugs, the shells sometimes remaining in the crypts. 

 There does not appear to be any definite line of division between 

 the two layers of ' marlstone.' The base of the ' marlstone ' is 

 alwaj'^s highly irregular, on account of the presence of large 

 branching and tubei'ous concretions of calcareous micaceous sand- 

 stone. The ' marlstone ' rests upon an impersistent stratum of 

 blue sandy clay, or directly upon the underlying Yellow Sands. 



(3) Details of Sections (Western Cliflfs). 



I think that it will be convenient to describe the sections from; 

 Down Cliff to Thorncombe Beacon before dealing with the ex- 

 posure at Watton Clift, east of Eypesmouth, which exhibits so 

 remarkably abnormal a facies as to call for special consideration. 



The following scheme of lettering of the several la3^ers of the 

 Junction-Bed and the contiguous deposits will be utilized through- 

 out the sections to be described below : — 



Scheme of Lettering. 



lilli C?J K. 



hifrons L. 



falciferum M.. 



'pve-falcifemm N. 



clay within Junction-Bed O. 



serrata P. 



Pleurotomaria (?) Q., 



spinatuin R. 



clay below Junction-Bed S. 



yellow sands T. 



D^imortieria 



Hammatoceras 



dispansum 



struchnanni 



pedicum 



A. 

 < B. 



C. 



D. 



E. 



F. 



G. 



eseri ... 



... H. 



striatulu'in 



I. 



variabilis 



J. 



thorncomhiensis U. 



Section I — The Junction-Bed and Contiguous Deposits, measuked 



hi situ NEAR THE WESTERN EnD OE DoWN CxIFF. 



Hemerae. 



Dumortierice. 



Lilli ?— 

 JBifrons. 



'Falciferum. 

 Syinattim. 



Strata and Fauna. 

 A + B. Blue sandy 'Upper Lias' clay. Coarse-ribbed 

 Dumortierice. 

 Impersistent irony scale. 

 K-fL. Pale conglomeratic limestone, with a very 

 smooth top. 

 midoceras bifrons, Dactylioceras cf, com- 

 mune, Wiynchoyiella. 

 [5217, a fissicostate Rhynclionellid, gen. et 

 sp. nov. ; 5211 a, Stohnorhynchia cf. bothen- 

 hamptonensis (Walker) ; 5211 b, St. cf. bou- 

 chardl (Davidson), but with too strong a 

 fold.] 

 Faintly-marked parting, 

 M. Yellowish limestone with red blotches. 



Harpoceras falciferum, Dactylioceras sp. 

 R. Oolitic conglomeratic 'marlstone,' with a very 

 smooth top. JBelemnites spp., Fseudopecten 

 cequivalvis. 

 T. Soft, yellowish, clayej^ sands. 



Feet 



inches 







CI 







2 



9 



7-8 

 6-9- 



