NO. 24 PTARMIGANIA STRATA RESSER 2"] 



In the pygidium fusion is not complete as ribs appear in the pleural 

 lobes. The axis is stout and long, terminating rather abruptly. Four 

 rings and a terminal segment are defined by shallow axial furrows. 

 As usual the anterior segment extends into stout spines directed 

 straight back and a small pair of spines is developed on the second 

 segment. 



Locality 54s. 



Holotype and paratypes. — U.S.N.M. Nos. o,8493a-c. 



PROZACANTHOIDES LIBERTYENSIS, n. sp. 

 Plate 3, figs. 13-15 



It is possible that two species are included in the illustrated material, 

 consequently one of the cranidia (fig. 13) is referred to the species 

 with reservation. All the material is fragmentary, but it seems worth 

 recording to show occurrence of Prozacanthoides in the Mill Creek 

 section. The description is confined to the holotype pygidium. 



The cranidium is parallel-sided, with a very slight expansion near 

 the anterior end. The dorsal furrow is clearly defined, rounding off 

 the anterior angles of the glabella. Palpebral lobes, which constitute 

 the fixigenes, are less than half the width of the glabella and the 

 eyes appear to have extended from the anterior pair of glabellar 

 furrows to the occipital furrow, with a rather even but not very 

 great curvature. Fusion is not complete in the pygidium and conse- 

 quently several segments are apparent. The border seems to lack 

 spines although it is wavy and has a strong indentation at the rear 

 of the axis. 



P. liberty ensis differs from the species in Two Mile Canyon by 

 its narrow brim and the pygidium, which has less detailed relief. 



Locality 59J . 



Holotype and paratypes. — U.S.N.M. Nos. (j8494a-c. 



PROZACANTHOIDES DECOROSUS, n. sp. 



Plate 3, figs. 16-18 



This species is represented by several examples of each part, and 

 is a particularly well-formed species. 



Four pairs of glabellar furrows arc: faintly indicated and the 

 widened neck ring carries a short, slender spine. The width of the 

 fixigenes is more than half that of the glabella, causing the glabella 

 to be rather slender in proportion. The eyes are long and fairly 

 evenly bowed with a slight decrease in curvature in the forward half. 



