Page:The Eurypterida of New York Volume 1.pdf/301

 palpebral lobes is supported by the fact that in the National Museum specimen this part projects prominently; further in all other species of Stylonurus the visual surface is a more or less narrow crescent on a circular base [see,   and  ], and it therefore should not be assumed to be circular in.

Some closer study of the eye region in the two carapaces of  has furnished the solution of these apparently contradictory facts in the finding of distinct, narrow crescentic, visual areas on the outside of the broken, circular, palpebral area. They are particularly well seen in the Rutgers College specimen, where they are clearly outlined although somewhat obscured by having become infolded at the collapse of the visual node.

We picture, then, the original aspect of the eye of  as a bulging subhemispheric, visual node, supported on the outside by the strong orbital ridge, on the inside by the median ridge of the carapace and the transverse palpebral lobes. At the apex of this node and at the outer end of the palpebral lobe the relatively small crescentic visual surface was situated.

It is obvious that the visual area did not keep step with the growth of the carapace and of the visual node and thus became finally a relatively small band around the apex of a high node. This giant merostome would thus seem to have possessed very small eyes in comparison with smaller eurypterids, a feature common in the giants of other groups, as in the whales and elephants among the mammals.

The collections from Schenectady and Duanesburg contain half a dozen specimens that are strikingly different from the associated eurypterids in greater relative length of carapace, broad, flat margin and subcentral position of the rather close-set large circular eyes, or eye nodes. All these characteristics suggest the generic reference of this interesting