pionis or Eusarcus in general, which is properly considered as a very aberrant eurypterid genus. But while the species is in almost all features an E. scorpionis, its distinctive characters are such as would indicate a still higher degree of aberrancy than seen in the considerably younger E. scorpionis from the Bertie waterlime. The most important of these characters are the tonguelike anterior process of the carapace and the position of the ocelli between the lateral eyes. The first would seem to be a further advanced adaptation to the mud-grubbing habit of the species, the snout being used as a digging and perhaps also a feeling organ.[1] The second character, the forward position of the ocelli in distinction of the still central position in E. scorpionis [see pl. 29] would also seem a further advance in the anteriorly raised carriage of the carapace peculiar to Eusarcus and indicated by the position of the lateral eyes and the forwardly progressing length of the walking legs.
Eusarcus cicerops, an Otisville species, has these two features, the anterior process and the forward position of the ocelli, in common with E. vaningeni. The former, in the position of the lateral eyes and the broad base of the carapace, seems closely allied to E. vaningeni, and as our specimens of E. cicerops are all of early growth stages, it is possible that the mature specimens were still more like E. vaningeni. The presence of these two closely related aberrant types in the lowest Salina beds of Oneida county and in the Shawangunk shale, strengthens our inference as to the probable equivalence of the Shawangunk grit with the Pittsford shale. Eusarcus nasutus
- ↑ The fact that this process is more or less bent downward in two of the specimens might lead to the assumption that it is homologous to the epistoma of Pterygotus and might have been bent under entirely. Several considerations disprove this assumption, namely, the absence of a suture separating it from the anterior part of the carapace and the passing of the filiform thickened border around the process; and above all, the existence of another species of Eusarcus (E. cicerops) with a similar but much less developed anterior process [see pl. 36, fig. 3, 4] which is clearly a straight extension of the carapace.
