Notices of Memoirs — Prof. Lajyicorih on the Ordovician. 79 



Shelve Series. 



(a) Stiper Group, consisting of the well-known Stiper Quartzites 

 and tlieir associated strata. 



(&) Ladijioell Qroup, composed of the dark shales and flagstones 

 of Myttou, Ladywell and Hyssington, with DichograptidcB 

 and Ogygia Selwynii, etc. 



(c) Stapeleij Volcanic Group, andesitic lavas, ashes and inter- 

 bedded shales. 



Meadowtown Series. 



(a) Weston Group of Grits, flagstones and dark shales. 



(6) Middleton Group, composed of dark shales, with Didy. Murchi- 



soni, and calcareous flagstones, with Ogygia BuccM and 



Asaplius tyrannus. 

 (c) Harrington Group, of intensely black shales, with Coenograptus 



gracilis and Leptograptus. 



CJhirburt Series. 



(a) Aldress Group, composed of the Sp^ Wood calcareous grit, and 



the Aldress Graptolitic shale. 

 (h) Marrington Group, including the Hagley volcanic ashes and 



shales, and the Whittery ashes and overlying shales. 



The only Ordovician rocks occurring east of the Longmynd are 

 those forming the local Caradoc Series of the author (the Caradoc 

 formation of geologists). The basement beds of this series rest 

 unconformably upon all the older rocks of the district — upon the so- 

 called Uriconian, Longmyndian, Wrekin Quartzite, and Shineton 

 Shales, and its component zones are each covered up unconformably 

 in turn by the basement beds of the Silurian. This isolated 

 Ordovician Series is composed of the following members : — 



Caradoc Series. 



(a) Hoar Edge Conglomerate, grits and limestone ; (b) Harnage 

 Shales ; (c) Chatwall Sandstone ; (d) Longville Flags ; and 

 (e) Onny, or Trinucleus Shales. 



The Shelve series answers generally to the strata commonly 

 designated Arenig ; the Meadowtown series includes the typical 

 members of Murchison's Llandeilo ; and the Chirbury and Caradoc 

 series correspond broadly to Sedgwick's Bala formation of North 

 Wales. 



Some of the most characteristic fossils of each of the Ordovician 

 sub-formations and zones were given, and it was shown how 

 naturally the physical and palasontological sequence agrees with that 

 of the corresponding Ordovician rocks of Britain and Europe. The 

 peculiar physical conditions of the Shropshire area in Ordovician 

 times, as indicated by the very different lithological characters of the 

 strata upon the opposite sides of the Longmynd, was pointed out ; 

 and the evidences for the geological horizons and relationships 

 of the volcanic rocks indicated in outline. In conclusion, it was 

 pointed out that the clearness and simplicity of the sequence, and 



