Page:The Eurypterida of New York Volume 1.pdf/352

 another characteristic set of striae is added posteriorly of the frontal set. The second set consists of curving striae running obliquely backward and inward from the antelateral angles and lateral margins [pl. 66, fig. 10] and connected by anastomosis with the frontal parallel line. Along the lateral margins they are dissolved into a meshwork of lines. Like systems of lines appear on the metastoma, where they pass transversely across, with a slight forward convexity, and on the coxa where they strongly anastomose. The coxal segments and the metastoma were also furnished with a fine striation.

Ontogeny. The ontogeny of  is well shown in the small series of individuals reproduced on plate 64. The most interesting of these specimens is the original of figure 1 which is but 2 mm long and very distinct. This larval form is a clear representative of the nepionic growth stage. It still lacks two, possibly three, segments of the full complement of twelve. Its most important feature is the remarkable general similarity to the mature stage of the species, in the slenderness and form of body, form of carapace and eyes and position of the latter. Its most distinctive larval characters are (1) the relatively greater size of the carapace, (2) the relatively great size of the compound eyes, (3) the smaller number of segments.

The carapace in the nepionic stage attains one fourth the length of the body, while in the ephebic stage it reaches only one fifth. The head is also broader than the rest of the body while in the mature specimens the greatest width is reached in the middle part of the preabdomen. It also seems that in this and the following growth stages the head is relatively somewhat shorter in outline than in mature forms (by about one eighth of the width) and slightly more rounded in front.

The compound eyes do not differ in location from those of the mature individuals, being intramarginal and separated by a small interval from the margin, but they are markedly larger, occupying one half the length of the carapace as compared with one fourth to one fifth in the mature stage. They are likewise distinctly more prominent; at least in the specimens representing the neanic stage.