HE species included in 

 this chapter form 

 several sub - orders, 

 the first of which is 

 the Myacea, agreeing 

 pretty closely with Cardiacea in the form of the gills 

 and the mantle, the variability of the mantle impres- 

 sion, and the want of uniformity in the union of the 

 gills. But the foot instead of being cylindrical is 

 more or less flattened from the sides, and more 

 tongue-shaped than finger-shaped. The shells gape 

 at one end or both, and this, as we have already 

 pointed out, is due to the fact that the siphons are 

 almost constantly extended, and consequently when 

 the shell is enlarged by normal growth these edges 

 are not permitted to come together. The subjoined 

 figure, showing the position of the Blunt Gaper 

 when alive, will help to explain this constant ex- 



e: 

 in 



