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The Pearl Oyster of the Gulf of Manaar: 
Avicufa (me/eagrina) fucafa. 
(By HENEY SULLIVAN THOMAS, Esq., M.C.S., F.L.S., F.Z.S.) 
There are numerous pearl bearers, some mai-ine, some fresh- 
water, some oysters, some mussels ; but the animal that 
yields the pearl with which we are most conversant, because 
of its being the pearl of the best lustre, is the pearl oyster 
of the Gulf of Manaar. 
In common parlance it has always been known as the 
pearl oyster, because the general form of the shell is that 
of an oyster, the valves being nearly semi-circular as in the 
common edible oyster (Ostrea edulis) of England, and not 
elongated as in the equally familiar edible mussel [Mytilus 
edulis) . The valves are also more flattened than in the more 
convex shelled common mussel aforesaid. The presence of 
a byssus, however, declares it to be a mussel; it belongs to 
the genus Avicula, and the growth of fine sea weed or fucus, 
with which the shell is covered, has presumedly given this 
mussel its distinctive appellation fiicata ; and the second name 
meleagrina, sometimes retained in brackets, is probably so 
retained to connect it with Lamarck's classification meleagrina. 
It is however now classed by Eeeve as Avicula, and is to be 
foimd in Tryon's Conehology, 1884, under — 
Class — Pelecypoda, his name for Lamellibranchiata. 
Order — Asijphonida. 
Sub-order — Heteromyaria, often included in Monomyaria. 
Family — Avic u lidce . 
Sub-family — Aviculince. 
Germs—' Avicula. 
Species— -4 yectt/ff {meleagrina) fucata. 
M 
