>Dear List:
>
>First of all; happy new year to everybody.

And to you too.

>I have a question, well, I am wonder how Provocator shells deposit
>enamel near the protoconch. Does the animal cover the entire shell
>when alive?? ( I noted they are entirely glossy ).

I have never bothered to observe a living specimen (I just GLOATINGLY
kill them for their shells... horrible me), but the mantle will be
responsible for much if not all of the glaze. However I doubt that
the mantle spends much time covering the entire shell. Have a close
look at a specimen (mine are not accessible now) and see whether
there are any linear irregularities in the glaze... such would be
caused by the mantle edges during deposition if the mantle cannot
cover the entire shell; I very much doubt it can, and the glaze will
be deposited bit by bit as the shell grows.

>  Which is the purpose, for
>example in Provocator mirabilis to glaze the protoconch and even
>deposit a prong over it??

Most specimens, particularly in the south, do not produce this apical
spike (Zidona dufresnei also produces just this type of structure).
The dorsum of the foot may be involved in producing this, but I
really don't know. However if the mantle produces the spike, it can
probably extend to cover MOST of the shell. What purpose does the
spike have? Possibly none... not every character in an organism has a
purpose. Typically such an inductural structure would be produced by
an enrolled tube of mantle tissue.

>Is the external shell layer named inductura?

Yes, but only in those forms where the outer layer is a secondary
deposit secreted over the normal primary surface of the shell. In
most forms with external inductura only part of the shell is covered;
these deposits may become very thick.

>which shells have them apart of Volutids?

Only a few volutids have this, and I am unsure wether the other
Provocator spp have it. It is not an uncommon condition.

>Tibias maybe??,

Some examples of taxa with external inductura:
Bellerophontoidea:
-Sinuitidea: Sinuites entirely covered, probably naticid-analog
Xenophoridae:
-Xenophora (Onustus) has broad flange lined on underside with inductura
Struthiolariidae:
-Struthiolaria (Tylospira) -  terminal varix coated with inductura
extends a full whorl
-Conchothyra parasitica (late Cretaceous) entire shell covered in adult only
Strombidae:
-Lambis lambis may have a broad thin deposit
Various Stromboidea:
-several extinct genera in various families
Cypraeidae
Ovulidae
Triviidae
Buccinidae: Nassariinae:
-Bullia can have sutural deposits
Harpidae:
-Harpa (could be considered to be an overgrown parietal shield)
Olividae:
-Ancillinae -  callus deposits on upper half of shell, covering spire
-Olivancillaria, Oliva, Agaronia - spire callus with pseudosuture
Volutidae:
-Ampulla priamus
-Cymbium some spp entirely coated
-Notopeplum sericata
-Provocator mirabilis
-Zidona dufresnei
Marginellidae:
-Afrivoluta pringlei & many others
Cysticidae:
-Persicula

>which is the name of the external layer on Cypraeidae?

Again, inductura.

I hope I haven't contradicted myself too much here...
--
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
<[log in to unmask]>
Seashell, Macintosh, VW/Toyota van nut

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