514 CEENELLINiE. 



Genus MYRINA, H. and A. Adams. 



Shell transverse, oblong, sub-equilateral ; valves closed, 

 covered with a brown, horny epidermis, pearly within ; 

 beaks sub-central. Hinge edentulous; ligament internal, 

 linear. Muscular impressions far apart; pallial line sim- 

 ple. Byssiferous. 



Ex. M. pelagica, Forbes, pi. 121, fig. 2. Shell, M. 

 pelagica, fig. 2, a, 2, b. 



The shell on which Ave have established this genus was 

 found off the Cape of Good Hope attached to floating 

 masses of blubber. 



Sub-fam. CEENELLIN^E. 

 Hinder part of mantle produced, forming false siphons. 



Genus CRENELLA, Brown. 



Mantle closed anteriorly ; anal tube perfect and produced. 



Shell equivalve, sub-orbicular or oblong, tumid or com- 

 pressed ; surface of valves covered with an epidermis, and 

 either entirely or partially ornamented with strioe radiating 

 usually in two diverging fasciculi from the beaks. Hinge- 

 margin toothless, generally crenulated; ligament linear, 

 internal. Muscular scars two, unequal ; pallial impression 

 obscure. 



Sy?i. Myaparo, Lea. Stalagmium, Conrad. Nuculo- 

 cardia, D'Orb. 



Ex. 0. discors, Linnaeus, pi. 121, fig. 3. Shell, C. de- 

 cussata, Litinieu*. fig. 3, a, 3, b. 



