S. W. Ford—New species of Primordial Fossils. 421 
exceedingly convex. The head is broadly semi-elliptical, wider 
than long, the length to the breadth about as 5 to 6. Con- 
and posterior portions of the border. The surface of the head, 
including the border, is transversely crossed by numerous faintly 
impressed lines, curving baicwandl for the most part invisible 
to the naked eye. 
The pygidium is of equal length and width with the head. 
The convexity, however, is a trifle greater along the middle, 
d 
to the angles. The contour of the sides and posterior margin 
the same as that of the sides and anterior margin of the head. 
harrow marginal border similar to that of the head, though 
not tuberculated, surrounds the pygidium, terminating on either 
side of the concave portion of the anterior outline. The sur- 
face 1s covered with delicate lines similar in character and 
direction to those of the head. : 
_ The two extremities are connected by a single thick thoracic 
ning. This ring is partly shown in fig. 1. From the appear- 
ance of the figure, owever, there would seem to be room for 
* Fig. 1. A nearl j limit of 
ze y perfect specimen of Agnostus nobilis. T . 
the head is not well shown in the figure, but may be made out clearly in oo 
cim 
on the border are wanting in this igure owing to their removal on the side of the 
presented. 
