One of the more pronounced states is that the front of the facial sutures do not cut the lateral or frontal border on its own, but coincide in front of the glabella, and cut the frontal border at the midline.
12.
The course of the facial sutures from the front of the visual surface varies at least as strong as it does in the rear branche, but the lack of a clear reference point similar to the genal angle makes it difficult to categorize.
13.
Many characters that are divergent from other trilobites may be explained by paedomorphosis, such as the small number of thorax segments and proparian facial sutures, that occur in all trilobites during larval development, while the Eodiscoid abatochroal eye is not unlike early development stages of the holochoal eye, where lenses are also separated.
14.
Trilobites have facial sutures that run along the margin of the glabella and / or fixigena to the shoulder point where the moults of trilobites can often be told from the fossils of the actual animals by whether the librigena are present . ( The librigena, or cheek spines, detach during moulting . ) In ptychopariids, short bladelike genal spines are often present on the tips of the librigena.
