I was pretty excited to finally see one of the Caloplaca squamosa group in person. I've long wondered what this bizarre microscopic character is that I've read about in the Caloplaca key in the Sonoran Flora so often: "layer below hypothecium paraplectenchymatous, round cells in apothecial margin". Turns out it's perfectly obvious when you finally see it. Yay. "Normal" Caloplaca have indistinct cellular structure under the hypothecium and narrow long radiating hyphae in the margins. This specimen had big round cells on the margin between the hymenium and the algae-filled portion of the rims. They gradually lengthen and become narrower as you move in from the margin, then grade into a tangle of tiny randomly-arranged hyphae under the hypothecium. Photos, however, didn't turn out well.