This trilobite so closely resembles Chasmops but is a related species, Pterygometopus.
Coming from the Middle Ordovician Asery Level deposits near Saint Petersburg,
Russia, this is a rarely-seen Russian trilobite. The species Pterygometopus is
recongnized as such by the unique glabellar furrows. Notice the fine pustules
found on the glabella and the cephalon. Eye facets are present as well, though
they are not as pronounced as those seen on many Moroccan trilobites of the later
Devonian era. The trilobite would be 1.8 inches long (measured along the curve)
if prone and 0.9 inches wide at the genal spines. The second trilobite is an Asaphus
cornutus, 2.5 inches long (along the curve), and 1.3 inches wide. Finally, there
is a complete cystoid of the genus Echinosphaerites (1.2 inches in diamter) present
as well.
