The picture below of a polished face of a Mixon Alveolina Limestone pebble has been achieved by stitching together about 60 photomicrographs at X20 magnification taken with a USB microscope. The file size is large to allow zooming in (three successive clicks on the image eventually brings up a highly zoomed in high resolution image). Some digital enhancement has also been used, and other pictures of this pebble on this website give a truer, more natural colour rendition.
The alveolines are taken to be Alveolina fusiformis (Sowerby), and their wide morphological variation has previously been noted by C.G. Adams in Alveolina from the Eocene of England (1962). Adams left open in that publication the possibility that Alveolina elongata (d’Orbigny) was actually a variant of fusiformis.