came across this in the side of a banking. it looked to be just a black stain but when i cleaned it the detail became more apparent. It was about 150mm wide and had a 10mm grove all the way up. the horizontal lines you cansee are all protruding. Found near Ramsbottom.
Nice specimen, but are you sure it is Artisia?
I am not familiar with the interwoven structure.
The example of Artisia shown on p.231 (plate 466, B) here is much simpler
I would be most interested if you have a link to an ID'd specimen showing that interwoven structure (please).