158 
PALEONTOLOGY OF NEW YORK. 
from the axial line to the margin, and may represent processes on the lower 
surface of the test designed for the attachment of the basal joints of the 
swimming feet or of the muscles moving those joints. 
Dimensions. The specimen here described has a length of 28 mm., a width 
of 30 mm., and a height of 5 mm. The distance between the posterior 
extremities of the eyes is 16 mm. 
Observations. This species is described from a specimen of the cephalon 
preserved in a block of sandstone and retaining the normal convexity of this 
part. Although only this fragment of the animal is known, it appears to be 
distinctly different from any species of Eurypterus heretofore described, and its 
specific validity rests upon the following features; (a) the convexity of the 
head-shield; (b) the anterior position of the eyes; (c) the ocelli, situated 
further back than is usual; (d) the flattened summit of the cephalon; (e) the 
oblique linear depressions on the postero-lateral area. 
Distribution. Clinton group. In the greenish sandstones from the northern 
part of Cayuga county. 
STYLONURUS, Page. 1856. 
Stylonukus excelsiok. 
PLATE XXVI. 
/Stylonurus excelsiw (Stylmmmis in eri’or), Hall (Martin). Trans. N. Y. Acad. Sciences, vol. ii, 8. 1882. 
Stylonurus excelsior. Hall. Thirty-sixth Ann. Kept. N. Y. State Mus. Nat. Hist., p. 77, pi. v, fig. 1. 1883. 
Stylonurus exeelsic/r. Hall. Proc. Ainer. Assoc. Adv. Sciences, vol. xxxiii, p. 421. 1884. 
Compare Dolichocephala Lacoana, Claypoi.l. Proc. Anier. Phil. Soc., vol. xxi, 236, plate. 1883. 
Cephalon elongate, semi-ovate; length to greatest width as 6 to 5. Basal 
margin transverse; baso-lateral angles truncate; lateral margins curving 
gently outward from the base, thence sloping more rapidly forward to the 
narrow anterior extremity. Surface depressed-convex. 
Eyes large, circular, closely appressed, situated just in front of the greatest 
transverse diameter of the plate and separated by a prominent median ridge. 
Each eye is encircled on its outer edge by a conspicuous, sub-semicircular 
