The title pretty much sums it up. I've reviewed every publication I can access, still having much trouble with what first appeared to me to be an easy I.D.
As you can see, the material has typical striated lines on its outer surface. On each striated line, there are "dots" from one end of the line to the other. Horizontally, the dots match up with the dots on the left and right of the striated lines beside. It would seem identifiable to me based on that type morphology, but I just can't find an example with such morphology.
Please help with this tough I.D. and thank you all in advance for viewing the specimen.