of the presence of a Eusarcus in the Otisville fauna, and therefore as supporting the reference of the species here described to that genus.
The carapace of E.? cicerops, as exemplified by the holotype, corresponds to that of Eusarcus in the following characters: its typically sub triangular outline with slightly projecting cheeks, the oval form and highly anterior marginal position of the compound eyes. The great width of the preabdomen is also a feature comparable only to Eusarcus.
The immature aspect of the holotype has been mentioned in the preliminary description. It finds its most distinct expression in the relatively large, oval eyes, their forward position and the prominence of the ocelli. It is shown in this paper that the earliest growth stage of Eurypterus maria, and to some extent also of members of other genera, is distinguished by its broad carapace, and thus the form of the head of E.? cicerops also emphasizes this impression of immaturity. It is, however, to be noted that while the specimens are quite probably not mature forms, their size excludes them from the larval or nepionic stage, of which the immature features mentioned here are characteristic. Moreover we have a specimen of larval dimensions and features [pl. 36, fig. 9] whose size indicates that the other specimens are at least of neanic age. If this be correct, they allow a fair conclusion as to the mature form which, as the largest of the specimens [pl. 36, fig. 2] indicates, retained the outline of the head and the position of the eyes, but lost the pearllike prominence of the eyes and the sigmoidal curvature of the lateral margins. The scarcity of the young individuals in the Shawangunk grit at Otisville allows the inference that the species was very rare in that fauna and adults have therefore not yet been obtained.
The carapace of the nepionic specimen [pl. 36, fig. 9], measuring but 1.2 millimeters, is of striking, or rather grotesque appearance by virtue of the following features:
- The broadly triangular outline
- The spinelike prolongations of the frontal and genal angles
- The immense, diverging eyes
- The strong median crest
- The broad margin
