Carapace relatively very broad and short, its length to width as 6 : 10–11; the character of the margins as in E. lacustris; the lateral eyes relatively small (one fifth of length of carapace), in front of center, far apart, halfway between median line and lateral margin. Ocelli not seen.
Abdomen. The preabdomen is contracted in both specimens, in the second less than in the type. Its length is to its width as 2 : 3+. It probably contracted more rapidly at the last tergites than the associated species of Eurypterus, but not so much as the two specimens, in which the last sternites are somewhat shoved together would indicate. The tergites have not been seen, except the first in the hypotype, specimen 2, where it is a narrow band, 11 times as wide as long. The operculum and other sternites apparently do not differ from those of E. lacustris except in being relatively somewhat wider.
In the type specimen the postabdomen occupies four ninths of the length of the body without the telson; it is about one fifth longer than wide at its beginning and its total length surpasses its anterior width by about one fifth. At the posterior extremity it has decreased to one third of its anterior width. The first segment is about four times as wide as long, the last is one seventh longer than wide. Its most striking feature is the long alae, resembling those of E. fischeri in relative size and form. Like the latter they were probably somewhat variable.
The telson spine occupies in the type but little less than one third of the length of the body, as against more than one fourth in the other species. Although the abdomen is contracted, it is manifest that the spine is relatively long. Otherwise it does not differ from that of E. lacustris. It is five times as long as its anterior width.
Appendages. But one (the third) endognathite has been seen, its last four segments projecting beyond the head shield. In the type the basal portions of all endognathites are withdrawn under the carapace and have been artificially exposed. The endognathite exhibits four spines on its fifth, five on its sixth and four on its seventh segment, all of which seem
