52 



[ Senate 



Stropiiomena ( Strophodonta) beckii ( n. s.). 



Pal. N.Y. Vol. iii, pi. 22, f. la - It. 



Shell siibsemicircular or subquadrate ; Iciigtli sometimes equal to 

 the width (though usually from two-thirds to three-fourths as 

 great) : ventral valve depressed - convex j beak very small : 

 dorsal valve flat or a little concave near the hinge, slightly 

 convex near the front : hinge-line crenulated, generally equal 

 to the greatest width of the shell, but sometimes less; area 

 linear, confined to the ventral valve ; foramen small, open or 

 closed. Surface marked with fine, regular, closely arranged, 

 bifurcating, radiating stride, crossed by fine obscure concentric 

 lines, and small more or less regular concentric wrinkles which 

 curve outwards on approaching the hinge. 



This species is very closely allied to Strophoinena {LeptcE7ia) soiverhyi 

 of Barrande ( Sil. Brach. aus Bohmen, pi. 21, f. 1 & 2 a, 1), c, e)j but 

 differs from those figures in being more coarsely striate, with the concentric 



SiaOPHOMEKA BECKII. 



