26 CATECHISM OF CONCHOLOGY, 



of the shell. This conformation is beautifully 

 adapted to the motion of the valves, and to the 

 construction of the hinge. 



Q. From what is the name of this genus 

 derived ? 



A. From a Greek word signifying kneading- 

 trough, though we can trace but little resem- 

 blance. 



