MYA. 



projects far beyond it at tlie posterior extremity, covering 

 the two long combined tubes which the animal projects 

 through the sand, one for the passage of the water to the 

 branchiae, the other excretory. 



We do not hesitate to unite Turton*s Genus Sphenioy 

 because it only differs a little in the size of the tooth in 

 the sinistral valve., which is not so much dilated, nor so 

 prominent as in the ordinary Myae, 



Shell transverse^ nearly equivalve, gaping at both ends, 

 but in a greater degree at the posterior end, with a single 

 large, compressed, dilated, vertically projecting tooth in 

 one valve ; the other valve without any teeth. Muscular 

 impressions two, lateral, distant ; the anterior rather 

 narrow, and the posterior nearly orbicular. Muscular 

 impression of the mantle with a large sinus. Ligament 

 internal, large, fixed to the prominent tooth in one valve, 

 and to a large subumbonal cicatrix in the other. 



