Plate 1 



Pycnaspis splendens, new genus, new species. 1, 2, USNM 21333, holotype, from Upper 

 Ordovician, Rock Creek section, Johnson County, Wyo. : 1, detached exoskeletal plate, 

 somewhat incomplete, showing tubercles of early and subsequent stages of growth, super- 

 ficial view; 2, same, oblique lateral view. 3-6, USNM 21336, from same layer and locality 

 as the holotype, detached ridge-scale oriented (3-5) with its anterior margin upwards: 3, 

 lateral view; 4, external view; 5, basal view; 6, posterior view. Magnification: 1, 2, X 32; 

 3-6, X 24. Explanation of symbols: bf, basal face; 0(ia, anterior portion of external face, 

 overlapped by the ridge-scale in front; ogi, lateral faces, overlapping adjoining polygonal 

 plates; ogp, posterior face, overlapping the ridge-scale following next behind; ta, tubercles 

 belonging to early stages of growth; tb, tubercles belonging to subsequent stages of growth. 



