164 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



narrow and elevated at the palpebral lobe; postero-lateral limbs 

 long and retaining nearly the same width from the glabella to their 

 outer side, which is rounded at the genal angle; palpebral lobes 

 small, elevated, and situated opposite the anterior end of the glabella. 



Free cheeks large, elongate, convex, with the eye lobe at the inner 

 anterior angle. 



The facial sutures cut the postero-lateral margin in advance of the 

 genal angle and pass obliquely inward to the base of the small eye 

 lobes, over which they curve before passing forward to the anterior 

 margin. 



Thorax with 23 segments; axial lobe convex, with each segment 

 rounded and prominent ; pleural lobes flat for a short distance from 

 the dorsal furrow, and then arched downward ; pleural furrows short 

 and narrow; segments rounded at the end of their broad faceted 

 surface. 



Pygidium small, transverse ; axial lobe short and divided into two 

 or three rings by transverse furrows that are continued across the 

 pleural lobes to their outer margin. 



Surface marked with very fine granulations and a few large 

 granules that are prominent on the glabella, frontal border, and 

 segments of the thorax. 



Dimensions. — The largest dorsal shield has a length of 9 mm. and 

 a width of 6 mm. at the base of the cephalon. 



Genotype. — Millardia semele Walcott. 



The generic name is from Millard County, Utah. 



Stratigraphic range. — Millardia semele occurs in the Weeks forma- 

 tion of the Upper Cambrian of Utah, M. optata in the lower part of 

 the Upper Cambrian in the Eau Claire formation of Wisconsin, and 

 M. avitas in the Upper Cambrian of Pennsylvania. 



Geographic distribution. — Millardia semele is from Millard 

 County, western Utah ; M. optata is found in western Wisconsin, near 

 Hudson, St. Croix County, and M. avitas is from Pennsylvania. 



Observations. — The cranidium of Millardia is much like that of 

 Dresbachia and Menomonia (pi. 26). It differs from both mainly 

 in the character of the frontal limb and border, and also from 

 Menomonia in having about one-half as many thoracic segments. 

 All three genera have the facial sutures cutting the border of the 

 cephalon in advance of the genal angle, and all agree in the eyes 

 being situated opposite the anterior end of the glabella. 



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