70 
ENCRINURUS TRENTONENSIS, Walcott. Syn. 4. punctatus. 
This species from the ‘'renton Group of Wisconsin was described 
from the pygidium; it has 23 axial joints, with nodes on the 3rd, 6th, 
roth, 14th, 18th and 22nd, with 9 pleurae. 
ENCRINURUS NEREUS, Hall. From Niagara Group, Racine, Wis. 
This species, described from a tail, has 18 axial joints and 8-9 pleu- 
rae. ‘The rings of the axis are distinct and not notched at the sides. 
ENCRINURUS EGANI, Miller. From Niagara Group at Joliet, Illinois. 
Plate GL, tie, 14) 
The genal anges are spined; glabella clavate and gibbous; projects 
in front beyond the narrow rim. Thorax 11; segments grooved, 
Pygidium a little wider than long, with caudal spine. 
Axial joints 18, with centre row of 4 nodes on the 4th, 7th, r1th and 
14th joints, Pleurae, 6, 
This group of species from the Clinton Group, consisting of Z. orna- 
tus and Threcheri with Egani, and Nereus from the Niagara Group, vary 
slightly in the number of axial joints, 18 to 20; and in the pleurae from 6 
to g: all of these species probably belong to the same species, and should 
take the older name, that of 2. neveus, Hall. 
Encrinurus Americunus, Vogdes, from the Clinton Group of Georgia, 
which has 20 axial joints and 5 or 6 pleurae, belongs to the same group. 
ENCRINURUS SEX-COSTATA, Salter. Plate II, figs. 1-12. 
Cybele sex-costata, Salter, Mem. Geol. Sur., vol. 2, pt. 1, plate 8, fig. 10, not fig. 
9, 1848. 
Zethus sex-costata, McCoy, Synops. Pal. Foss. Woodw. Mus., fasc. 1, p. 156. 
fncrinurus sex-costata, Salter, Mem. Geol. Sur., Decade 7, plate 4, figs. 1-11. 
Brit. Pal., Rocks & Foss, Appendix A, 1855, p. iv. plate 1G, figs. 6-7. 
Nieszkowski, Archr. Nat. Liv. Ehst. Kurl, 1857, p. 80. 
—Vogdes, Mong. genera Zethus, &c., p. 25, plate 3, figs. 1-12. 
General shape, broad ovate head, and tail convex; body rather flat; 
head triangular; genal angles produced; the front rounded, gibbous and 
overhanging. Glabella pyriform; it overhangs the margin; there is a 
strong furrow which runs across the front of the glabella, separated from 
it by a thick, prominent ridge (fig. 3a); it has three short lateral furrows. 
The cheeks, though convex, are much less so than the glabella, and 
bear the eyes in the middle, the surface pitted with fine granules. ‘Ihe 
free cheeks have their outer margin thick and separated by a furrow, with 
the genal angles produced into spines. 
The posterior margin has a strong neck furrow continued along it. 
Thorax with rr segments; each pleurae is nearly semi-cylindrical, with a 
row of 3-4 tubercules along its centre; tips bilobed., 
Pygidium triangular, wider by one-third than the length, with obtuse 
rounded anterior margin. Axis with 20 joints extending across it, but 
