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MC
Hi everyone, 

We found these over the weekend in Seven Sisters. We've only just started learning to identify fossils and we'd appreciate some guidance :-)

(1) We're quite sure this one is a sponge? 
IMG_20190717_152718.jpg  IMG_20190717_152728.jpg  IMG_20190717_152745.jpg

(2)  We're wondering if this one could be a fossilised shell?IMG_20190717_152302.jpg  IMG_20190717_152309.jpg  IMG_20190717_152329.jpg

(3) And this one we're not sure about... is it just a natural mark? 
IMG_20190717_152158.jpg  IMG_20190717_152207.jpg  IMG_20190717_152226.jpg  IMG_20190717_152236.jpg 

Many thanks,
MC    
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Brittle Star
Hi

Photo 3 is a possible sponge. Not familiar with area, someone will know.
JW

 Never ask a star fish for directions
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TqB
Welcome to the forum!
I can't see anything that looks like sponge structure in the first one, though there may be one inside. It seems to be a flint nodule with characteristic impact marks.
The second one really does look like a fossil but I think it's nice a piece of banded flint (try searching that) - it's very good at looking like shelly bits!
The third one though is a beautiful piece of sponge in what looks like chalk (if it's soft enough). [smile]
Tarquin
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prep01
Hello, I think I can see a sponge in the 1st one - annotared below, but as Tarquin says, it's a very well rolled flint.

Untitled.png 

The second one as said is banded flint and lastlyI think more Chert than flint (same chemical make up).
Colin Huller
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MC
Thank you all so much for your replies!

About the third one, the sponge in chalk: what is the explanation for the long striped band? It looks very different to the spotted area. I'm not sure how to visualise the complete volume.
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Weald on Bed
The striped band is the 'holdfast'. The area of the sponge where it attaches to the substrate. Because of how your fossil has eroded, you're seeing some of the holdfast in oblique section, hence why the stripes vary in length.
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TqB
It's a piece of wall of a vase or sheet shaped sponge, the stripes being the cross section view. I don't think there's any holdfast there, which would consist of long, thin strands.

Something like this maybe: 
IMG_3444.jpeg 

And the morphology of a simple vase shaped one from Wikipedia:
Screenshot 2019-07-19 at 12.34.30.png 
Tarquin
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MC
Sorry, I forgot to reply to this -- the figures are extremely helpful, especially the first one. Thank you very much for the explanation!
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