30 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
CHEIRURIDAE Salter. 
CHEIRURINAE Raymond. 
CHEIRURUS NIAGARENSIS (Hall). 
Plate 4, fig. 1 se 1) SHES 
Ceraurus insignis Hall, Pal. N. Y., 1852, 2, p. 303, pl. 67, f. 9, 10. 
Ceraurus niagarensis Hall, 20th Rept. N. Y. state eab. nat. hist., 1868, p. 376.. 
? Whiteaves, Geol. surv. Canada. Pal. foss., 1884, 3, pt. 1, p. 42; 1895, 
3, pt. 2, p. 107. ? Van Ingen, School of mines quarterly, Columbia univ, 
1901, 23, p. 35 (no description). Kindle, 28th Ann. rept. Dept. geol. and 
nat. res. Indiana, p. 483, pl. 23, f. 1, 2, pl. 24, f.8. Weller, Bull. Chicago 
acad. sci., 1907, no. 4, pt. 2, p. 263, pl. 24, f. 20, non 21. 
The name Ceraurus niagarensis appears for the first time on p. 376 
of the first edition (1868) of the 20th Ann. Rept. of the New York 
State Cabinet of Natural History. Earlier in the same paper, (p. 335), 
Hall referred certain trilobites from the Silurian at Wauwatosa and 
other localities in Wisconsin to Ceraurus insignis (Beyrich). On 
p. 376 he states that he has reexamined the specimens and considers 
them different from C. insignis. The name Ceraurus niagarensis is 
used as a heading, but is not designated either as a new name or a new 
species. On p. 427 of the Revised edition, published in 1870, the 
remarks are reprinted, but the letters N.S. follow the name. In 
neither case is there any description of the species given, but the 
plates contain representations of an imperfect cranidium and a broken 
hypostoma. 
The next use of the name by Hall was in 1879, in the 28th Rept. of 
the N. Y. State Museum, p. 189. He here describes the pygidium at 
some length from specimens obtained at Waldron, Indiana, and 
remarks, at the end of his description: “From the above it will be 
seen that the separation first made in the revised edition of the 20th 
Rept. St. Cab., was necessary, and that it constitutes a distinct spe- 
cies.” The single figure given represents a pygidium. 
After studying collections from a number of localities it becomes 
evident that the American forms now referred to Ceraurus niagarensis 
include two or three species, and it is therefore, necessary to determine 
the type for C. niagarensis. From the absence of description accom- 
