The Wing Shells, Pearl Oysters and Hammer Oysters 



By a Strange chance, the species discovered since the genus 

 was first built up on the characters of M. vulgaris, have, with the 

 exception of M. alhus, lacked the peculiar double-winged pro- 

 longation at the hinge. The others are headless hammers, with 

 valves of considerable irregularity of form. However, the name 

 stands, describing the largest and most important members. 



400 



