LAMP-SHELLS AND THEIR ALLIES 19 



it may be, is not the only opportunity for healthful 

 existence. 



The last member of the brachiopod family to be 

 described is closely related to some of the shells 

 which are found in the oldest of the fossil- 

 iferous rocks. Perhaps, therefore, it has a 

 pedigree reaching back farther than that oi 

 any other shell in the world. Its name is 

 Glottidea albida. Hinds, the White Tongue- 

 shell, and it is shown in Figure 9. It has 

 been collected at Monterey, and it extends 

 to the shores of Lower California. I once 

 gathered a few specimens from the mud 

 flats of San Pedro, which were left bare by a low 

 tide. A friend instructed me to dig where I saw 

 little narrow slits in the surface of the mud. I 

 obeyed, and found that the little creatures were 

 buried in holes, the tips of the shells being just be- 

 neath the surface. A flesh}^ stem, longer than the 

 shell, reached down into the mud, and served as an 

 anchor. In the picture you can see the remnant of 

 the stem, curled and dry. When the tide returned, 

 I dare say the creatures rose a little and began gath- 

 ering minute particles of food from the water. The 

 shells are smooth, thin, and when freshly gathered 

 are more brown than white. Exposed shells, how- 

 ever, soon bleach. Unfortunately for shell-gatherers, 

 the old collecting grounds at San Pedro have been 

 largely spoiled by the dredging operations by which 

 the shallow bay is being made into a good harbor 

 for ships. 



In olden times the lamp-shells were more abun- 



