30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



west of Montpelier, Idaho; Z. spinosus is from Mount Stephen, in 

 British Cokimbia, 685 miles north-northwest of Spence Gulch. 

 Among the associated fossils are Bathyuriscus hoivelli Walcott, 

 Oryctoccphaius reynoldsi Reed, Oryctocara geikiei Walcott, Micro- 

 mitra (Iphidella) pannula (White). 



Formation and Locality. — Middle Cambrian : Spence shale of 

 the Ute formation, 2,755 feet (839.7 m.) below the Upper Cambrian 

 in the Liberty Can_von section ; Spence Gulch, a ravine running up 

 into Danish Flat from Mill Canyon, about 15 miles (9.37 km.) west 

 of Montpelier, and 5 miles (3.12 km.) west-southwest of Iviberty, 

 Bear Lake County, Idaho, U. S. A. 



Genus NEOLENUS Matthew 

 NEOLENUS INFLATUS, new species 



Plate; 5, Figures 1-5 



Dorsal shield large, elongate-elliptical in outline ; axial lobe 

 strongly convex. Cephalon semicircular in outline, with the genal 

 angles produced into sharp spines about one-half the length of the 

 cephalon ; a narrow, rounded rim extends across the front of the 

 cranidium, and, widening a little, runs along the outer margins of 

 the free cheeks to the genal angles. The facial sutures cut the 

 posterior margin well within the genal angles with an outward 

 direction to the posterior furrow, where they curve inward and 

 forward to the base of the eye lobe ; arching over the eye lobes they 

 curve outward to about the line of the outer rim of the palpebral 

 lobe, forward to the frontal rim, and then obliquely inward across 

 the rim to the front margin. Cranidium with a prominent, tumid 

 glabella, narrow fixed cheeks, small antero-lateral limbs, and strong 

 postero-lateral limbs. Glabella large, convex ; the frontal lobe is 

 inflated and, in all but young, small specimens, overhangs the frontal 

 rim ; the sides gradually expand from the occipital ring to the 

 broadly rounded front, which extends forward to, and lies parallel 

 with, the furrow within the rounded frontal rim ; the anterior half 

 of the glabella is taken up by the expanded, anterior lobe and the 

 posterior half is divided into four narrow lobes by shallow furrows 

 that extend obliquely inward and slightly backward nearly to the 

 median line ; in some specimens, especially the young, the furrows 

 are very faintly defined ; occipital ring separated from the glabella 

 by a narrow, shallow furrow ; it is broad, moderately convex, and 

 with a strong, long, sharp, arching spine that extends back over the 

 thorax nearly to the pygidium ; the base of the spine occupies nearly 

 the entire width of the occipital ring at its center. Fixed cheeks 



