gS SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



there is the border and rim and in front of this the free cheeks add 

 a narrow part that merges into the front of the border. 



Free cheeks wide, with long strong genal spines: they appear 

 somewhat unusual because of the extra furrow necessitated in order 

 to fit on the front of the head. 



Associated pygidium large with the high, strong axis occupying 

 about half its length: border concave and considerably upturned in 

 some species. Three axial rings and three to four pleurae are out- 

 lined that merge into the broad border. 



Genotype. — Idahoia serapio Walcott. 



Range. — Upper Cambrian : Rocky Mountains of Idaho. 



Ob.'iervations. — Idahoia, during its study, was first regarded as a 

 relative of Saratogia, but the absence of glabellar and occipital 

 furrows, the wider fixed cheeks, the intramarginal suture and the 

 frontal limb give the genus vei^y distinctive characters. 



IDAHOIA MALADENSIS, new species 



Plate 19, figs. 13, 14 



Observations. — This species is represented by considerably less 

 material than /. serapio. It difTers from the latter in the greater 

 convexity of the border and rim. The glabella is also lower, with a 

 hint of two pairs of short glabellar furrows. 



The associated pygidium assigned to this species dififers from that 

 assigned to /. serapio in its somewhat broader, even more concave, 

 border and fewer pleural segments. 



Formation and locality. — Same as for Idahoia serapio. 



IDAHOIA SERAPIO Walcott 



Plate 19, figs. 1-12 



Idahoia serapio Walcott, 1924, Smithsonian Misc. Coll., Vol. 75, No. 2, p. 58, 

 pi. 14, fig. I. 



Observations. — The generic description, together with figures, pre- 

 sent most of the characters of the species. None of the free cheeks 

 is sufficiently well preserved to give a complete representation of 

 the anterior portion. The width of the doublure is indicated in 

 figure 4, where the upper shell is broken away. 



Formation and locality. — Upper Cambrian: (54w) Ovid forma- 

 tion. On the north side of Two Mile Canyon, two miles (3.2 km.) 

 southeast of Malad, Oneida County, Idaho. 



