As to its general form the hypostoma resembles that of the preceding species, but there is no border line, which is so characteristic to the former. The maculæ have the same form and are likewise situated on the median line. The cephalic eyes have prismatic lenses with much convex bases, in a transverse section they are hexaedral and of internal radiate structure.
Niobe Angelin.
The following figures have formerly been given of its hypostoma with maculæ.
N. emarginula Br. II tab. 2 fig. 33.
N. explanata Br. II tab. 2 fig. 35.
N. frontalis Br. II fig. 37.
N. insignis Br. I tab. IV fig. 1 d, 11 tab. 2 fig. 28.
N. læviceps Br. II pl. 2 fig. 34.
The maculæ are distinguished from all other sorts of maculæ, excepting those of Megalaspis, in being, as it were, shelved on a sort of support, formed through the bulging of the hypostomic surface just below them, one such console for each. Their surface lies consequently almost rectangularly to the adjoining surface of the hypostoma. They are white and smooth.
Niobe frontalis Ang.