258 NEW YORK STATE MUSEUM 
Eusarcus triangulatus nov. 
Plate 84, figures 7-9 | 
Nine carapaces which have in common the broad, short, subtriangular 
form and the forward position of the marginal lateral eyes, bear a close 
resemblance to the carapace of E. scorpionis from the Bertie 
waterlime. The largest of these [pl. 84, fig. 7], which is also the most dis- 
tinct, has been selected as the type of the species E. triangulatus. 
Description. Carapace broadly subtriangular in outline, twice as 
broad as long (length of type, 20 mm, width, 43 mm), the lateral margins 
gently convex in the anterior third, forming a blunt frontal angle. Pos- 
terior margin straight transverse or broadly convex forward; genal angles 
acute. The lateral eyes are marginal, situated one third of the length 
of the lateral margin from the frontal apex, small (one seventh to one 
eighth the length of the side), bean-shaped, the visual surface apparently 
occupying the entire node. No facets seen. Ocelli situated in the middle 
of the carapace. 
In several specimens the first tergite is found attached to the carapace. 
This 1s broad and short, about seven times as wide as long. In another 
specimen [pl. 84, fig. 9] the preabdomen and the proximal portion of a 
swimming leg are also preserved. 
The carapace and first tergite were smooth or have only small, scat- 
tered tubercles. 
Horizon and localities. The Frankfort shale (Schenectady beds) at 
Schenectady (Dettbarn quarry), Duanesburg and Rotterdam Junction. 
Genus DOLICHOPTERUS Hall 
Hall erected Dolichopterus as a subgenus of Eurypterus, citing as its 
distinguishing characters: the development of the “‘palette’’ (ninth seg- 
ment), the less dilatation of the natatory feet, the form of the metastoma, 
and of the ‘central footlike organ” (genital appendage). It has been 
accorded full generic rank by later authors, with perfect propriety, we feel 
