Wonderful, Of Troy, do you happen to know if the horseshoe crab's light-gathering lenses are crystilized in the same manner as the trilobites,i.e. with a tri-axial alignments which helps the sensor cells determine the direction of the incoming light? Interestingly, the horseshoe crab is considered a modern relative of trilobites. Not a direct descendent but maybe a second cousin back in the good old days of the Ordovician, back before the big kill off at the end of the Paleozoic. According to Richard Fortey, female trilobites probably had their egg sacs in their heads as do the horseshoe crabs of today. Richard reports that he was served Limulus eggs (the only eatable part of the horseshoe crab) in Thailand. He said that inside the head section of the crab were big yolky eggs. The horseshoe crab eggs tasted rancid and intense. He thought that his beloved trilobite's eggs would have tasted sweeter,