NO. 3 CAMBRIAN TRILOBITES 169 



Stratigraphic range. — Norwoodia saffordi: Upper Cambrian ; 

 Nolichucky shale. 



Norwoodia gracilis, N. simplex, and A'', ponderosa: Upper Cam- 

 brian ; Conasauga shale. 



Norzvoodia tenera: Upper Cambrian ; Weeks formation. 



The above indicates that as far as known the genus had quite a 

 prolonged existence in Upper Cambrian time. 



Geographic distribution. — Eastern Tennessee, northeastern Ala- 

 bama, and the House Range of western Utah. 



Observations. — As known to me now, this genus is an unusual 

 form that has hitherto escaped observation. It probably originated 

 in the Atlantic or the Appalachian Sea, where it attained its greatest 

 development ; one species, N. tenera, is a somewhat modified species 

 from the Cordilleran area of western Utah. 



The species from Alabama were collected for me in the Coosa 

 Valley by Dr. Cooper Curtice in 1885. The stratigraphy of the 

 Conasauga formation is so difficult to work out, owing to faulting 

 and flexing of the shales and interbedded limestones, that the exact 

 stratigraphic position and vertical range of each species are unknown, 

 but I think that the genus is of Upper Cambrian age and mostly of 

 the horizon of the upper Conasauga formation in Georgia and Ala- 

 bama, and the Nolichucky shale in Tennessee. 



NORWOODIA GRACILIS, new species 



Plate 27, figs. 2, 2a-g 



General forrh of dorsal shield a broad ellipse with large genal 

 spines extending backward and outward nearly as far back as the 

 pygidium. 



Cephalon convex, roughly semicircular ; marginal border strong, 

 moderately convex, and continued into the strong genal spines ; 

 posterior border narrow, and separated from the fixed cheeks by a 

 strong furrow that merges on each side near the genal angle into 

 the strong intramarginal furrow of the cephalon. Glabella small, 

 rounded conical, and marked by three pairs of short glabellar furrows 

 on each side ; a shallow occipital furrow defines a median occipital 

 ring that has a long, slender spine extending back from the posterior 

 center of the ring; frontal limb large and gently convex to the 

 intramarginal furrow ; intramarginal furrow usually clearly defined ; 

 frontal border flattened or slightly convex; postero-lateral limbs 

 large and bearing a strong, slender, slightly curving spine at the 

 genal angle. 



