94 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



Dimensions. — There are nine entire specimens of the dorsal shield 

 exclusive of the free cheeks. The average length is 15 mm. The 

 different parts have the following dimensions : 



Cephalon: mm. 



Length 6.5 



Width at posterior margin 9 



Length of glabella and occipital ring 5 



Width of glabella at base 3.5 



Thorax: 



Length 7.5 



Width at first segment 8 



Width at last segment 5 



Pygidium: 



Length 2 



Width at anterior margin 4.5 



Observations. — This species is the only one of the genus Anomo- 

 carcUa of which we have specimens showing the cephalon, thorax, 

 and pygidium, with the exception of the compressed dorsal shield of 

 AnoniocarcUa chinensis. The cranidium differs from that of the 

 type of the genus, A. chinensis, in having a relatively smaller pal- 

 pebral lobe, and twelve segments, instead of eight, in the thorax. 



Formation and locality. — Middle Cambrian ; (90X) Conasauga 

 formation ; in and attached to the outer surface of siliceous nodules 

 m argillaceous shales, Coosa Valley, east of Center, Cherokee County, 

 Alabama. 



Collected by A. M. Gibson, 1884; and Cooper Curtice, 1885. 



Genus COOSIA, new genus 



The description of the genotype Coosia snpcrba and the observa- 

 tions accompanying it may be taken as the description and discussion 

 of the genus. 



Genotype. — Coosia superha Walcott. 



COOSIA SUPERBA, new species 



Plate 16, figs. I, la 



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

 medium width, conical, and narrowing from the cephalon gradually 

 to the middle of the pygidium where it disappears. 



Cephalon semicircular in outline, moderately convex, genal angles 

 unknown. The facial sutures cut the posterior margin some distance 

 within the outer margin and extend inward and forward with a 

 slight sigmoid flexure to the base of the palpebral lobe ; arching about 



