Dalman had drawn attention to the weakly defined axial furrows in the Ordovician trilobite " Nileus ".
2.
The " Treatise on Invertebrate Paleontology " describes " Euproopidae " as " small forms with wedge-shaped cardiac lobe bordered by distinct axial furrows, abdominal shield with annulated axis bearing a high boss on last segment . " The same source describes " Euproops " as follows . " Prosoma with flat genal spines and carinate opthamalic spines; cardiopthamalic region with or without intercardiopthamalic area; abdomen with raised pleural ridges that cross flattened rim and are prolonged as marginal spines; annulated axis with knob on 1st and 3rd segments and elevated boss or short spine on hindmost segment; telson long ."
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