160 
PALEONTOLOGY OF NEW YORK. 
drawing which accompanies this description has been made from a plaster im¬ 
pression of this natural mould. 
The cephalon in S. excelsior is more elongate, the anterior extremity narrower 
and the orbital ridges very much more prominent than in any other known 
species. It has an axial length of 252 mm., and a width of 223 mrn., or a 
length of about ten and a width of about nine inches. It undoubtedly repre¬ 
sents one of the largest of palaeozoic Crustacea, probably the largest known with 
the exception of Pterygotus angUciis. By comparison with the other species of 
Stylonurus, S. Logani, and S. Powriei, Woodward, of which the length is known 
either from entire specimens or approximate restoration, it appears that S. ex¬ 
celsior would have measured, when entire, upward of fifty inches in length. 
Distribution. Catskill group. Andes, Delaware county. 
Stylonukus (?) (Echinocaris? ) Wrightianus. 
PLATE XXVII, FIGS. 7-9. 
Equisetides Wrrghtiana, Dawson. Quart. Jour. Geol. Soc., vol. xxxvii, p. 301, pi. xii, fig. 10; and pi. xiii, 
fig. 20. 1881. 
Equisetides Wrightiana (Dawson), Hall. Thirty-fifth Kept. N. Y. State Mus. Nat. Hist.: Expl. pi. xv. 
Note, and figs. 1 and 2, (Tj-ansmitted, 1882). 1884. 
Echinocaris Wrightiana, Jones and Woodward. Geological Magazine, Dec. iii, vol. i. No. 9, p. 3, pi. xiii, 
figs. 1, a and b. 1884. 
Echimcans Wrightiana, Etheridge, Woodward and Jones. Third Kept. Committee on Fossil Phyllopoda 
. of the Palaeozoic Rocks, p. 35. 1885. 
Cephalothorax unknown. 
Abdomen. The original specimen consists of two somites, each being sub-cylin¬ 
drical and flattened on the dorsal and ventral surfaces; the anterior somite 
somewhat the shorter and broader. The anterior margin of each somite is 
elevated into an articulating ridge, which is shown to the best advantage 
upon the posterior segment, as the overlapping edge of the preceding joint 
has been broken away in such a manner as to expose it. The dorsal and 
lateral surfaces of each segment bear a series of sharp longitudinal ridges 
which extend for nearly one-half the length of the segments. These ridges 
themselves do not appear to have extended far beyond the posterior margins 
of the segments, but they may have served as the bases of attachment of 
