74 UPPER CAMBRIAN (ORDOVICIAN). 



In the neighbourhood of Haverfordwest the following divisions 

 in the Bala Series have been made by Messrs. J. E. Marr and T. 

 Roberts :^ — 



rSlade Beds. — Gritty green shales, seen at Lower Slade, with 



Tnmicleus seticornis, Phyllopora Hisingerii, etc. 

 Redhill Beds. — Bluish-grey shales, seen near Redhill Farm, with 

 Trinudeus Phacops Brongniartii, etc. 



seticornis -l Sholeshook Lwiestone. — Greenish impure limestone and calcareous 

 Beds. shales of Sholeshook and Prendergast, with Trinudeus seti- 



cor7tis, Phacops Broiigiiiartii, Heltolitcs iitterstindus, etc. Siauiv- 

 cephalus globiceps occurs here and also in the Rhiwlas limestone, 

 with which it is compared. 

 Roheston Wathen Limestone. — Black limestone and black shales of Robeston 

 Wathen, with Halysites catenulai-izis, Orthis etegantttia, etc. The bed is 

 compared with the Bala and Coniston Limestones. 

 Dicranograptus Shales. — These beds succeed the Llandeilo limestone of Llandewi 

 Velfrey, and consist of black shales, with bands of grit, and are usually crowded 

 with Graptolitesof the "tuning-fork " type, \nc\wdmg Dicra nog raptns rainosus, 

 Chniacograptiis bicornis, etc. The uppermost portion of these shales is 

 spoken of as the zone of Orthis argentea, being characterized by that 

 Brachiopod. 



In describing the great masses of "gnarled" shales or schists of 

 Anglesey, Prof. Hughes has suggested that they may be of the age 

 of the Bala volcanic series. They comprise greenish shales with 

 gritty and serpentinous bands, some much gnarled, others little 

 altered.* 



In Shropshire the Caradoc rocks have been thus divided:^ — 



Onny Shales. — Seen on the banks of the Onny, near Cheney Longville. 



Cheney Longville Flags. — Seen near the village of that name, near Winstanstow, 

 south of Church Stretton. 



Chatwall or LLorderley Sandstone. — Shelly sandstones seen at Chatwall, north- 

 east of Caradoc and Horderley. Orthis alternata. 



Harnage Shales. — Exposed near Harnage. Trinudeus concentricus (Trinudeus 

 Shales), Beyrichia coinplicata, Orthis testudinarta, Diplograptus, Fazv- 

 sites fibroszis, etc. 



Hoar Edge Grits. — Seen along Hoar Edge. Strophoviena expansa, Orthis 

 vesper tilio, . fla bellulum . 



These beds are overlaid unconformably by the May Hill Sand- 

 stone. (See p. 44, and Fig. 9, p. 58.) Shales, with Trinudeus con- 

 centricus, etc., occur at Bausley Hill (Breidden Hills), north-east of 

 Welshpool ; and these are underlaid by volcanic beds, and by the 

 unfossiliferous Criggion Shales.* 



In the Craven district, an indefinite area that lies between Settle 

 and Ingleton, the Silurian rocks rest unconformably on rocks of Bala 

 age. These latter comprise an upper series of limestones, shales, 

 mudstones, and ashy grits, containing fossils of Bala types ; and 



1 Q. J. xli. 478. 2 Q j^ xxxvi. 239. 



^ C. Callaway Q. J. xxxiii. 655 ; J. D. La Touche, Geol. Shropshire, p. 12 ; 

 J. W. Salter and W. T. Aveline, Q. J.xiii.2ii : Murchison, Siluria, edit. 5, p. 66. 

 * W. W. Walts, Q. J. xli. 533. 



