Dear friends,
I must apologize, I am a new Conch-L reader, and maybe I do not have
sufficient experience in what you seem to call 'shelling' ... no more than
60 years I'm afraid, of which only 50 as a professional. Most probably
that's the reason that I was most confused by Mr Campbell's reply
mentioning,among others, Miltha childreni.
For the first time in my life I read the word 'umbus' and I tried to find
out what it means, using the transcendental world wide web, inclusive of
wikipedia ... but at no clear result.
Finally, Google turned up with an almost unreadable text of Gould 1852, who
apparently wrote "
Interior silvery white, with a very
broad drab-white Umbuswhere he was describing 'Acephala'.
Obviously the 'umbus' is situated at the interior of bivalves ? Some other
Google results mentioned the word 'umbus' too, mainly commercial sites, but
most referred to 'Col-umbus', which didn't help me a lot. If 'umbus' was
mentioned in the context of Mollusca, it usually was connected with a
colour: umbus pink, umbus white and so on.
At my wit's end I decided to believe that what was meant with 'umbus' is
nothing else than what we usually call the 'umbo', or'umbones' in plural.
If so, why the heck does one use 'umbus' ??
Arie W. Janssen, Gozo, Malta
[log in to unmask]
http://users.waldonet.net.mt/ariewe/
Download my papers from: https://sth-se.diino.com/ariewjanssen/papers
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"brighter than glass, and yet, as glass is, brittle"
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----- Original Message -----
From: "David Campbell" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, July 14, 2010 5:28 PM
Subject: Re: [CONCH-L] Left handed shells
>> A few people know but it happens with bivalves too - for example Miltha
>> childreni. It has one of the valves flat - placing it down so the umbus
>> is
>> curved towards right. In a few cases (not so rare though), the umbus is
>> curved to the left.
>
> Two other versions of handedness in bivalves:
>
> In most cementing species (chamids, oysters, plicatulids, etc.),
> attachment is by one valve. For most groups, the attaching valve is
> consistent, but in some it is variable.
>
> The hinge teeth differ in the left and right valve. In some species,
> the tooth arrangement is reversed in rare individuals. At least one
> species, "Alasmidonta" heterodon, has a dentition reversed from other
> members of its family (hence the species epithet).
>
>
> --
> Dr. David Campbell
> 425 Scientific Collections
> University of Alabama
> "I think of my happy condition, surrounded by acres of clams"
>
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