FAUNAL SUCCESSION OF THE UPPER BERNICIAN 617 



Notes: — Cyathaxonia cornu and Caninia nov. sp. are 

 restricted to the Middle Skateraw Limestone in the Dunbar, 

 district, whilst ZapJirentis near oystermouihensis is abundant at 

 that horizon. These facts support the correlation of the 

 Acre Limestone and the Middle Skateraw Limestone made 

 by Gunn and Bennie.* 



Saccatiimina carferi is rare in the Five Yards Limestone, 

 but forms a conspicuous band in the Six Yards and Acre 

 Limestones (cf. Four Fathom Limestone). When, as often 

 happens, the matrix containing the foraminifera has perished, 

 the mass has the appearance of coarse oolitic limestone. 



The shale at the base of the Six Yards Limestone in the 

 Little Mill Quarry yields almost all the forms recorded here, 

 whilst most of the Acre Limestone forms were found in the 

 shale above the main calcareous bed at Ancroft. Chonetes zL 

 hardrensis is exceedingly abundant in the latter shale. S. 

 carbo?iarins was obtained at Snab Leazes Quarry near 

 Alnwick. 



The Four Fathom Limestone. 



(=Eight Yards Limestone of the Alnwick District and the 

 Lowdean or Sandbanks of the Lowick and Scremerston area.) 



Geographical Distribution. 



Same as that of Great Limestone. 



Stratigraphical Character. 



This bed shows great structural change as it is followed 

 from the south-west to the north. At Haltwhistle it consists 

 of over 40 feet of limestone remarkably free from argillaceous 

 intercalations, but contains numerous siliceous layers and 

 nodules of chert. Round Alnwick the Four Fathom Limestone 

 is about 30 feet in thickness and is composed of two calcareous 

 members separated by a band of black shale three and a half 

 feet in thickness. In the numerous chertose bands the upper 



* R, G. Carruthers, 



