CONCHIFERA OR BIVALVES. 117 



can be found alike, and the rarity of some 

 causes them to be very valuable, and much 

 sought after. Externally 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. 



75. Vulsella. — Shell longitudinal, tongue- 

 shaped, nearly equivalve, irre- 

 gular ; bosses equal ; hinge, with 

 a prominent callosity in each 

 valve, showing an impression 

 of a conical and arched pit for 

 the ligament, which is partly 

 external. Animal unknown, 

 without byssus. — 6 recent and 

 1 fossil species. 



These shells are not at- 

 tached, but are found buried 

 in sponge. They are irides- 

 cent within, and are brought 

 from the Indian Ocean and 

 the seas of New Holland. 



This genus was placed by Lamarck in the 

 Ostreidce family, but more modern naturalists 

 place it here. 



I 3 



