Unknown species from Indian ocean

[conchylinet]

Dear collectors,

I need help with the identification of these 4 shells from tropical Indian Ocean.
They all come from a same beach in Comoros near Moroni (Mozambique Channel).

4200 is a 17mm Arcidae (Barbatia?)
<img src="http://www.conchylinet.com/Images/Misc/4200.JPG" alt="http://www.conchylinet.com/Images/Misc/4200.JPG" style="border:0" />

4201 is a 15mm Arcidae
<img src="http://www.conchylinet.com/Images/Misc/4201.JPG" alt="http://www.conchylinet.com/Images/Misc/4201.JPG" style="border:0" />

4208 is a 12mm Nerita
<img src="http://www.conchylinet.com/Images/Misc/4208.JPG" alt="http://www.conchylinet.com/Images/Misc/4208.JPG" style="border:0" />

4218 is a 20mm bivalve (Arcidae?)
<img src="http://www.conchylinet.com/Images/Misc/4218.JPG" alt="http://www.conchylinet.com/Images/Misc/4218.JPG" style="border:0" />

I know it does not seem easy but any kind of help would be welcome.

Cheers
Conchylinet.  <span class="petit">--Last edited by conchylinet on 2008-12-18 04:48:37 --</span>