Tlic Fauna of the iMaxvillc Liuicstoiic 



371 



the beak and gradually increases in size to near the margin where 

 it rapidly expands into a trumpet-shaped opening. Hinge line 

 straight, of medium length, with medium sized auricular extrenv 

 ities. Surface marked by fine radiating plications, whicli in- 

 crease in number by bifurcation or insertion, and man_\- of which 

 decrease in number by coalescence at a point just j^osterior to 

 the expansion of the anterior margin. Auricular margins 



Fig. 8. — Productus pileifoniiis. 



a. — A view of a pedicle valve, the anterior margin of which is 



more or less broken. 



b. — A view of the internal portion of the umbonal half of a brachial 



valve and the external portion of the anterior half of the 

 pedicle valve. 



c. — Profile view of a specimen (with a broken beak) showing the 



trumpet-like expansion of the anterior margin of the shell. 



marked by prominent concentric wrinkles which (lisa[)pear at 

 the side of the shell so that the umbonal region is free from 

 them or so that the latter region is marked by only faint repre- 

 sentations of them. 



Brachial valve slightly concave in the umbonal region, sud- 

 denly reflected at the anterior margin to conform to the jDedicle 

 valve, into which it is deeply withdrawn. Interior ( ? ) surface 



