Ostrna c( irreoularis 



(^ryi>h eta. dumorti eri 



Qryphoea z^^ obliquata. 



Qryphc£a aff. incarua. 



Fig. 1. — Four members of the lineage of GrypJioea incurva, sliovving the leftvalve, 

 the shell as viewed from the posterior side, and the left valve in section. 

 The area of attachment is shaded, (a) Ostrcea of. irregularis Munst., 

 Lavemock Shales, Lavemock, Glam. (b) Grypha'O. cf. duwortitri Joly, 

 angulata su b-zone, Dunraven, Glam. (c) G. aff. obliquala Sow. , Vernnceras 

 sub-zone. Workhouse Quarry, Ke;ynshfim, Somerset, (d) G. aff. incurva 

 Sow., ? gm,uendense sub-zone, near Bridgend, Glam. (slightly reduced). 



