dejayM's picture

Flat Periwinkle geometry

Observed: 14th May 2013 By: dejayM
Biological Recording In ScotlandHighland Biological Recording GroupOrkney Biodiversity Records Centre
dejayM’s reputation in InvertebratesdejayM’s reputation in InvertebratesdejayM’s reputation in InvertebratesdejayM’s reputation in Invertebrates
fine shell
3 sorts
T.geometry 4
T.geometry 2
T.geometry 3
T.geometry 1
Description:

Trying to convince myself..
This post is linked to
http://www.ispot.org.uk/node/328587
In the geometry pictures the comparison is with the common Flat Periwinkle (L.obtusata)
See http://www.seawater.no/fauna/mollusca/fabalis.html - old name is L.mariae
Picture two also shows L.obtustata and L.saxatalis

Identifications
Species interactions

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Comments

trudy-russell's picture

your samples do seem quite

your samples do seem quite different , I recently spent a day looking at these (and other molluscs) down at Looe in Cornwall and we looked for the geometric differences and found some variation but nothing this clear!

Trudy Russell
Marine Advisor
Natural England

To find out about what's going on in the south west check out http://www.ispot.org.uk/forum/8409

dejayM's picture

leading lines

It's nice of you to come here Trudy (and give an agreement).
Mud though, isn't it.
I have a leading book - let's name it - Collins Pocket Guide (Hayward, Smith, Shields) the illustration on P189 should clinch it! Does it?
I think the separation of L.obtusata from L.fabalis is more to do with shell thickness, the top-whorl closeness and angle-to-apex line.
JoC may have nailed it here http://www.ispot.org.uk/node/328587#comment-111361
And this is the best illustration I have seen
(by far) http://www.seawater.no/fauna/mollusca/fabalis.html (old name) It is from THE leading book.
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