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Date: Wed, 10 Jun 1998 12:32:10 +0000
From: "ross mayhew." <[log in to unmask]>
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Organization: schooner
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To: Eddie Hughes <[log in to unmask]>
Subject: Re: Crenella species
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Dear Ed;
        Let's try this again- a "bus error" erased my first effort.  I don't
know about PC Land, but the busses in Macville are easily upset!!
        I apologise for not answering this queery earlier, since it is "up my
alley", as it were.  Anyway, there are two genera involved in Nw
Atlantic waters north of Cape Cod (my expertise ends there, where the
Gulf of Maine stops)- Arvella Scarlato, 1960 ex Bartsch, ms, and
Crenella Brown, 1827.  The former includes faba (Muller), and pectinula
(A. Gould), and is easily distinguished from Crenella by the markedly
assymetrical shape of the spp., even in small juveniles.  Faba is
uncommon, and occurs from NFLD south, while pectinula dominates in the
north.  The species you are finding on George's Bank is glandula (ok-
faba may occasionally be found in the area, in patches of fine sediment,
but only in the deeper areas, and is uncommon even there), which has an
almost symetrical shape, is ovate in shape, and grows up to 17mm,
usually 12-13mm or so.
        The real fun occurs when you find decussata and glandula together, as
is common in fine, organics-rich seds inshore.  Juvenile glandula, while
being just slightly less symmetrical than decussata, is so similar that
one sometimes must separate the valves in order to be certain- decussata
is shinier inside.  However, if you are counting large #s of both,
errors are nearly inevitable!!
 
        I would be happy to be of assistance regarding any spp of shell-bearing
marine molluscs north of Cape Cod.  We have less than 500 spp in total,
so it is possible to become familiar with most, exept of course those
troublesome Turridae, certain Buccinids, and the infinitely-pesky
Yoldiella clan.
                                                                                                                -Cheers,
                                                                                                                Ross.