758 THE PALEONTOLOGY OF MINNESOTA. 
(Harpina rutrellum. 
axial length of the shield, anterior extremity narrow and obtuse. Basal lobes very 
broad and large, together making the glabella considerably broader at the occipital 
ring than itislong. These lobes are separated from the glabella by short, posteriorly 
oblique lateral furrows, and from the cheeks by deep grooves which are abrupt and 
; 
Figs. 80, 81.—Portion of cephalon of Harpina rutrellum, with sectional outline showing the charac- 
ter of the doublure. 
ridged on their outer margins. The occipital ring is narrow, elevated and well 
defined over about one-half the extent of the cheek. Cheeks somewhat flattened 
above, abruptly deflected to the concave margin. Hyes small, nodiform, distant 
from the glabella and situated in a transverse line cutting the shield at its center. 
Surface of convex portion of shield covered with coarse, deep, irregular punctures 
which are coarsest about the eyes and on the anterior slope of the shield, become 
finer and more nearly circular about the margin. The glabella is covered with 
shallow, irregular pits, while the basal lobes and occipital ring are smooth. Doublure 
flat, its width equalling that of the concave part of the upper surface; thence it is 
bent upwards at a right angle, its distal portion becoming parallel to the anterior 
slope of the shield, as in the accompanying figure. The outer surface of the flat 
area is covered with large and very coarse circular puncte. Length of specimen 
9mm.; probable width at base, 16 mm. 
Though there is but a single example of the head, the characters above given 
are sufficiently distinctive. Whether a second specimen showing only the flat 
portion of the doublure belongs to the same species it is impossible to decide 
definitely, though the character of the punctation is essentially similar, and the 
vertical section shows that the upper surface was concave about the margin. 
Perhaps the species most closely allied to ours is Prof. Hall’s Harpes escanabe* from 
the Trenton horizon on the Escanaba river. This was based upon the marginal 
rim of a small cephalon described as being strongly pitted with the puncte arranged 
along the outer and inner edges of the finer and more abundant perforations in the 
middle. This agrees with the character of the wnder surface of the second of our 
specimens, but not with the upper surface of the first and more typical example. 
Harpina rutrellum may also be compared with H. antiquata Billings, of the Chazy 
limestone. 
Formation and locality.--The cephalon described is from the Galena beds at Cannon Falls, Minn. 
(Mr. Ulrich’s collection); and the fragment of the doublure is from the Trenton at Minneapolis (Museum 
No. 8420). 
* Foster and Whitney’s Rept. Geology of Lake Superior, p. 211, pl. xxv1r, fig, 2a, 1851. 
