96 



THE AMERICAN NATURALIST [Vol. XL 



1. Lamellosiiy of Growth Lines. — The concentric growth Hnes 

 become more closely spaced and lamellose, with a tendency to 

 pile up at the lateral and anterior l)orders of the shell. 



Examples: a pedicle valve of Laqueus californiciis Koch, No. 



715, up[]to and inclu<liiio- its mature <ir()\vtli, a U'ligth of 40 mm., 

 has only one or two strongly marked growth lines, while on its 



