Page:The Eurypterida of New York Volume 1.pdf/314

 the neanic position of the eyes and the round anterior angles and stands in the proportion of length to width between the neanic and nepionic stages as 10 : 15.

The submarginal position of the compound eyes in the neanic stage is a feature inherited from the preceding stage and corresponding to the appearance of these eyes in the larva of Limulus at the line of insertion of the rimlike edge of the lateral lobes [text fig. 24]. A peculiar difference, apparently at variance with the enormously enlarged eyes in the larval condition between the neanic and ephebic stages consists in the relatively smaller size of the visual surface and inclosed node in the former [cf. fig. 9, 11 with pl. 52, fig. 2, 3]. But if, as we have inferred before, the final visual node and visual surface in the nepionic stage are represented by the central or apical node borne on the large larval visual node, then the small size of the eye in the neanic stage is the direct result of the nepionic condition. We have then the peculiar fact, that in the ontogeny of  the actual visual surface of the eye increases relatively with advancing age, while the visual node on which it is borne, greatly decreases.

The ocelli have not been located in the nepionic stage, but their position midway between the lateral eyes in the neanic stage can be clearly made out.