ITo face page 114. 



GEOLOGICAL STAGES. 



Tertiary ... 



CUETACEOUS.l 



/ Wealden 



Jurassic 



RWiETIC- 



:!A. 



Brit 



SOUTH AMERICA. 



ESTHERI^. 



Trias 



Permian 



Cahboniferous 



Sussex. I 



( Oxfordian, 



( Lower Ool: 



Linksfield, 



Warwicksh 



Gloucester! 



. Somersetsl 



' Leicestersh 



Warwicksl] 



Worcesters 



. Somersets! 



Rhone Mil 



stern " 

 forth 



Cacheuta 



Estheria Middendorfii {1) . 



(Estheria elliptica, and E. elliptica, var. suh- 

 I quadrata. 



(Estheria Murchisonice, E. concentrica, and E. 

 i, Kotahensis. 



(Estheria minuta, var. Brodieana, E. Manga- 

 l liensis (?), E. ovata (?), and E. Forbesii (?). 



'Upper Cof 

 Manchei 



Coal-measi 

 and Lan 



Lower Cat 

 wickshii 



Oi.i) rtEn Sandstone 



\_Leaia^ occu 

 Coal-meas 

 shire, and 

 ferous of I 



Caithness 



Lower 

 Penu 



Estheria minuta. 



Estheria Portlockii, E. tenella, and E. exigua. 



Estheria tenella and E. striata and its varieties. 



' No fossil Ust/ieria are as yet re 

 ' The adoption of this stage for 

 ^ See the Appendi.\. 



Estheria membranacea. 

 Siberian and the South American Ustheria described above being of this age. 



