Got my 62.5cm specimen today. An impressive shell. It arrived at work
and when I showed it to my paleontologist/lecturer boss he
immediately wanted a pic of me holding it for his 1st-year lectures.

The operculum is tiny (relative to the size of the shell, that is).
Looking at the growthlines on this, it is apparent that the operc
changes shape during growth, becoming proportionally narrower and not
keeping pace with the growth of the aperture, therefore no longer
being able to seal the shell. No doubt this is due to the animal's
outgrowing any potential predators, so the operc is then only needed
as a pad on which to rest the shell (large prosobranch shells,
including fossils, often show wear near the parietal shield caused by
this). So I assume that this operc is the one belonging to this
particular shell. It will look odd mounted in the shell... with a
ROLL of cottonwool.

I can see why the species was placed in Melongeninae for so long...
the fuzzy periostracum of my juvenile specimen strongly resembles
that of Volema (Pugilina) morio.

As I have nowhere to put it at home, I guess I'll have to keep it at
work... in a showcase in our paleo/geology museum.

Someone on the list mentioned straight vs twisted canals in this
species. This big shell has a quite straight canal.
--
Andrew Grebneff
Dunedin, New Zealand
64 (3) 473-8863
<[log in to unmask]>
Fossil preparator
Seashell, Macintosh & VW/Toyota van nut
________________________________
I want your sinistral gastropods!
________________________________
Opinions in this e-mail are my own, not those of my institution
_______________________________________________
A: Because it reverses the logical flow of conversation.
Q: Why is top posting frowned upon?