69 
Some Ludlow specimens have the glabella narrower, and but 4 nodes 
down the axis of the tail. (Salter.) 
The variety called avenaceus Salt. differs only in the abrupt ending 
of the tail, which has not the long caudal spine of &. punctatus, but the 
terminal joint of the axis of the tail is deflected and blunt. 
ENCRINURUS VIGILANS, Hall. Plate III, figs. 17, a, g.° From Trenton 
Limestone of New York. 
The head is more than semi-lunar in form, with its genal angles pro- 
duced into long spines extending to the tail. ‘The glabella is not lobed 
The front lobe is thickened and marked with 2 rows of tubercles. Eyes 
facetted, prominent. 
Thorax with 11 segments; the axis has on every second joint a node 
or short spine. 
Pygidium triangular, with 9 pleurae, every alternate one being orna- 
mented with a node. Axisof 18 joints, every third one being marked by a 
node. 
The specimen has only 18 axial joints in the tail, and a longer 
spine to the genal angles of the head, than the type E. punctatus, and 
should be compared with &. Seedachz, Schmidt. 
ENCRINURUS ORNATUS, Hall & Whitfield. Plate ITI, figs. 15, rsa. 
The authors refer Cybele punctatus, Hall, Pal. N. Y., vol. 2, p. 297, 
plate 66a, figs. ra-e, to this species. Pal. Ohio, vol. 2, p. 154. 
The Clinton specimens from New York have a subcresiform head, 
with the genal angles produced into spines extending to the fourth thor- 
acic segment. Glabella clavate, also tuberculated; plate 66a, fig. 1, shows 
two lateral furrows. Thorax with 11 segments. 
Pygidium triangular; no caudal spine shown in illustrations.» Axis 
of 20 or more joints, notched at the sides, centre with row of 6 nodes, 
located on the ist, 4th, 8th, 13th, 17th, 20th axis joints. 
Other specimens from Clinton, at Lockport, have 7-8 pleurae, with 
5 nodes on the axis of the tail, viz: on the 7th, rrth, r5th, roth and 23d 
joints. These nodes occur at variable intervals, but with sufficient irregu- 
larity to discredit the value of such features for specific distinctions. 
Pleurae 7-8, marked with a central row of 3 or more tubercles. 
The Ohio species, £. ovatus, is of larger size; it has 20 axial joints, 
7 pleurae iu the tail, with 5 nodes on the 2nd and 5th joints, the three 
others having three segments between each node. 
E,NCRINURUS THRECHERI, Foerste. 
In the Proc. Boston Soc. Nat. Hist., vol. 24, p. 269, the author places 
this species with Hall's E. ornatus under E. punctatus. 
The species has 13-18 axial joints and 7 pleurae in the pygidium, 
with nodes on the 5th, 8th, rith, rath, 15th and 18th joints. 
