155 



the Australian Seas. This rare shell is practically confined 

 to the Ironstone of Eston and Upleatham Hills, but specimens 

 have been obtained at Boulby and Roseberry Topping. Not 

 only is it of great rarity but it is seldom found with both 

 valves in opposition.* 



The Brachiopoda, or Lamp Shells, are not uncommon in 

 the Ironstone Beds though scarce in the North Sea to-day. 

 The familiar Rhynchonella tetrahedra is very abundant and 

 frequently occurs in pockets, whilst Terebratula is also 

 numerous. Table No. 3 shows the fauna of the Ironstone 

 Series of the Middle Lias. 



Table III. 



Census of the Fauna of the Ironstone Series of 

 the Middle Lias. 



Total 



121 



59 



In the Upper Lias, we meet with another distinct group of 

 fo?sils. New genera of Ammonites, Stephanoceras, Phyllo- 

 ceras, and Harpoceras abound together with many unique 

 bivalves, such as Inoceramus dubius from the Jet Rock ; Leda 

 ovum and Trigonia literata, from the Alum Shale. Fishes 

 are comparatively numerous in the jet shales, and com- 



* Mr. T. W. Saunders, of Saltburn, has a beautiful and perfect 

 specimen found by him in Boulby Mines. 



