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. 



''inns. 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. 



Stylonurus excelsior. 



PLATE XXVI. 



Stylonurus excelsior (Stylomurus in error), Hall (Martin). Trans. N. Y. Acad. Sciences, vol. ii, p. 8. 1882. 

 !ts excelsior, Hall. Thirty-sixth Ann. Kept. N. Y. State Mus. Nat. Hist., p. 77, pi. v, fig-. 1. 1883. 

 Stylonurus excelsior, Hall. Proc. Amer. Assoc. Adv. Sciences, vol. xxxiii, p. 421. 18S4. 



ire Dolichocephala Lacoana, Claypoi.l. Proc. Amer. Phil. Soc, vol. xxi, p. 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 



