42 MULTIVALVES AND BIVALVES. 



however, only eleven species are claimed as British, we may as 

 well give the list : 



TESTICARDINES 

 Terebratulid ae 



Terebratulina caput serpentis. 

 Terebratula capsula. 

 Waldheimia cranium. 

 Waldheimia septigera. 

 Terebratella spitzbergenensis. 

 Argiope decollata. 

 Cistella cistellula. 



Rhynconellidae 



Atretia gnomon. 

 Rhynconella psittacea. 



ECARDINES 



Craniidae^- 



Crania anomala. 



Discinidas 



Discinisca atlantica. 



For the purposes of identification we can tabulate these genera 

 as follows : 



Shell without hinge 



Foramen in ventral valve Discinisca. 

 No foramen Crania. 



Shell with hinge- 

 Loop reflected 



Loop attached to septum Terebratella. 

 Loop not attached to septum 



Shell smooth 



Loop small Terebratula. 



Loop large Waldheimia (as regards cranium}. 



Shell striated Terebratulina. 



Shell ribbed Waldheimia (as regards septigera). 



Loop not reflected- 

 Shell semi-ovate and ribbed Argiope. 

 Shell without ribs or striations Cistella. 



No loop, but short, curved crura 

 Foramen beneath beak 

 Black in colour Rhynconella. 

 Not black in colour Atretia. 



As for our own convenience we arranged our illustrations in a 

 way peculiar to ourselves, it is desirable that we should here give in 



