CONCHIFERA. 



309 



ternally the appearance is very rude and irregular ; but, on 

 the other hand, the interior is exceedingly beautiful, being 

 lined with the most brilliant mother-of-pearl. 



Crexatula. Lam. — Shell nearly equivalve, irregular, 

 foliated, flattened: hinge straight, marked with a few 

 semicircular excavations which 

 contain the ligament ; no dis- 

 tinct opening for the byssus. 

 Animal unknown. — Few spe- 

 cies. 



This shell, which is thin and 

 fragile, is lodged in sponges, 

 and is brought from India and 



Australia. The byssus has not been seen, and therefore 

 it is not positively ascertained whether it possesses one ; 

 there is no passage for it as in the next genus. The 

 pearly portion of the interior of the valves is very irides- 

 cent, but scarcely covering half the shell. 



Melixa. Retz. (Perna Brug. ; Sutura Megerle and 

 Muhlf.; Hippochasta Sangio- 

 vanni.) — Shell nearly equivalve 

 and flat, irregular, with an open- 

 ing for the passage of the bys- 

 sus; bosses small; margins very 

 brittle : hinge straight and 

 broad, with parallel grooves for 

 the ligament. Animal, with the 

 mantle entirely cloven ; the foot 

 similar to Avicula } and bearing 

 a coarse byssus. — Few species ; 

 also fossil. 



From India, the Cape de Verde Islands, &c. ; generally 

 found moored to rocks deep in the sea, and occasionally 



x 3 



Mdina epJiippium. 



