The maculæ, seen in a thin section from the inside, are reticulate, [fig. 49], or of a pattern exactly like that in the changed eyes or maculæ of Illænus and even Asaphus, and thus indicating that it was composed of short prismatic lenses. The vertical section of a macula of a specimen from another locality rather suggests the presence of large sphærical lenses than elongated prisms. The great thinness of the macula in contrast to the excessive thickness of the shell around the eye is seldom so evident as here.
A specimen of an unknown species, found detached, has the macula? unlike the other species, oblique with the inferior end directed inwards, placed on the top of a sort of a little elevation, [fig. 47].
Megalaspides Brögger.
This author has a figure of M. dalecarlicus in II pl. 1 fig. 19 and also of an unnamed species fig. 20, both showing globular maculæ. In Holm's original description of his Megalaspis dalecarlicus (Trilobiten des Phyllograptusschiefers Dalecarliens figs. 8, 9) the same hypostoma is also figured. This genus seems to have a closer affinity with Ptychopyge than with Megalaspis.
Megalaspis Ang.
The following figures of hypostomas with maculæ have been published.
Megal. limbata by Brögger I, tab. XII, fig. 10, and in II pl. 2, fig. 22, somewhat differing from the first figure.
Meg. planilimbata Brögger II tab. 2 figs. 21, 21 a. Both figures incomplete and incorrect.
The hypostoma has a large central ovate gibbosity with the maculæ near its basis, surrounded by the winglike expanded limbus.