EXPLANATION OF PLATE 3 E. 



1 AVICULOPECTEN SEGREGATUS (M^Coy). Left valve, natural size. 



2 AVICULOPECTEN CONCAVUS (APCoy). Left valve, natural size. 



2 a Part of surface magnified. 



3 AVICULOPECTEN CANCELLATULUS (INPCoy). Left valve, magnified three diameters. 

 S a Outline, natural size. 



4 AVICULOPECTEN RUTHVENI (M^Coy). Left valve, natural size. 

 .5 AVICULOPECTEN C.-ELATUS (]M<^Coy). Left valve, natural size. 



5 a Portion of surface, magnified. 



6 AVICULOPECTEN DOCENS (M'Coy). From carboniferous limestone of Lowick. Left valve, 



natural size, internal cast, shewing the long cartilage facet, (without central pit) along the hinge-margin ; 

 also the pallial and muscular impressions. 



7 Var. from Derbyshire, with remarkably straight and regular ridges. The radiating ridges are 



effaced on the ears of this specimen, but by changing the light may be seen as described. 



8 AVICULOPECTEN PLANORADIATUS (M-'Coy). Left valve, natural size, of specimen broken 



along the ventral margin. 



9 PINNA SPATULA (M'^Coy). Left valve, natural size; from tlie carboniferous limestone of 



Derbyshire. 



9 a Section near anterior end. 



9 b Profile near posterior end. 



10 Smaller and more perfect specimen from Lowick, Northumberland. 



11 PINNA FLEXICOSTATA (M-^Coy). Left valve, natural size ; from Lowick. 



1 2 Right valve. 



13 Section of both valves. 



