>Dear Andrew,
>
>I think we've limited the confusion over spiral (radial) and
>collabral (concentric) sculpture with this exchange.
>
>Since the shells the ID over which Marcus is puzzling are neither
>Eocene nor deep-sea, I guess the field is a bit reduced. Do you wish
>to hazard a guess on shell characters alone?
>
>Harry

Hi Harry

I guess I could... if you'd like to send me the URL, which I haven't
kept. Unless it's <www.wonderphotos.com/shellphotos/lepetidae.jpg>...
for which it's definitely a Pectinodonta (Acmaeidae). If this is the
image in question, then judging by Okutani 2000 it appears to have
lower ornament than P. orientalis (Schepman 1908), though lighting
can play tricks. Okutani's descriptions are generally unhelpful.

The image strongly resembles P. aupouria Marshall 1985 from NZ, but
on the flanks of the species in question the collabral (axial,
"concentric") sculpture appears to be weaker than the spiral cords.
As Marshall points out, like P. aupouria, it is more acutely conic
than P. arcuata and P. rhyssa. Marshall compares P. aupouria with
several species of which I am unfamiliar, P. maxima (Dautzenberg), P.
gilbertvossi Olsson and P. alta (?authorship). P. rhyssa is lower and
more elongated.

Similar specimens from Madegascar have been sold by dealers .

It might be worth mentioning that shells of the shallow-water
tropical neritoid genus Phenacolepas can strongly resemble
Pectinodonta, though in this genus the apex is closer to the
posterior margin than the apex of Pectinodonta is to the anterior
margin.

Thanks
Andrew

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