Page:The Eurypterida of New York Volume 1.pdf/120

 Nepionic and neanic stages [ pl. 51, fig. 1–13]
 * 1) Larger carapace
 * 2) Broad, flat border of carapace
 * 3) Distinct glabella
 * 4) Larger eyes (very large ocular nodes)
 * 5) Eyes nearer to margin
 * 6) Segments not differentiated
 * 7) Smaller number of segments
 * 8) Smaller telson
 * 9) No distinct ornamentation

These lists of ontogenetic characters permit the following general inferences:

1 The carapace is relatively larger in the larval stages; often very much so. This is especially marked in the representatives of Pterygotus, Hughmilleria and Stylonurus. It is also recognizable in the young of ; the few young specimens of   are also suggestive of a larger size of the carapace but not conclusively so, since the preabdomen of the specimens is probably accidentally contracted. In  the carapace is distinctly shorter and wider than in the mature stage. This is in accordance with the entire character of this larval stage which in its broad carapace and broad short preabdomen, anterior divergent eyes and rapid contraction of the preabdomen distinctly exhibits the characters of the genus Eusarcus. The young carapace of  indicates no relatively larger size although the single individual available may be already too far advanced to still exhibit this difference in size.

The shieldlike character of the carapace is sometimes still emphasized by a broad flat margin, as in Stylonurus and  (?).

2 The compound eyes are relatively much larger than in the mature stage; and sometimes borne on more prominent ocular nodes. The larger