NO. 24 I'TARMIGANIA STRATA RESSER 39 



PTARMIGANIA NATALIS, n. sp. 



Plate 4, figs. 13-18 



This is perhaps the most abundant species, but a pygidium has not 

 been located for it. The glabella is long, expanding rather evenly 

 but slowly forward with the usual four pairs of furrows visible. The 

 neck spine is long and extends up from the neck ring. The fixigenes 

 are confined largely to the palpebral lobes and at their widest points 

 are almost exactly equal to half of the glabellar width at the same 

 point. The eyes are long, extending from the occipital furrow to the 

 third pair of glabellar furrows, and the eye band is continued to the 

 glabella by a large, wide eye ridge. The eyes are evenly bowed, in- 

 creasing their curvature slightly toward the rear. Forward of the 

 eyes the fixigenes form a flange about twice the width of the brim. 

 Brim confined to a rim slightly upturned and striated. The fixigenes 

 are very convex with the platform setting at a 60° angle to the border, 

 thus sloping steeply down from the eye. Surface evenly granulose 

 except in the depths of the furrows. 



Locality 54s. 



Holotype and paratypes. — U.S.N.M. Nos. 985i6a-d. 



PTARMIGANIA ORNATA, n. sp. 



Plate 4, figs. 25-32 



This is another common species represented by numerous cranidia 

 and libragenes, but no pygidium has been located. The glabella is 

 nearly parallel-sided and long, with the usual four pairs of furrows 

 and the occipital furrow is clearly shown. The cranidium is highly 

 arched longitudinally with a fairly even curvature. In cross section 

 the glabella is quite convex, also with an even curvature. The libra- 

 genes rise very steeply from the dorsal furrow before they turn over 

 to the eye lobes as is shown in figure 30. The occipital spine is long 

 and erect. The eyes are rather strongly bowed and the palpebral lobes 

 at their widest points are less than half the glabellar width. This is 

 perhaps the most granulose species, the granules being large and 

 numerous, wanting only in the depths of the furrows. 



Locality 54s. 



Holotype and paratypes. — U.S.N.M. Nos. 9850/a-f. 



PTARMIGANIA AGRESTIS, n. sp. 

 Plate 7, figs. 1, 2 

 This species is represented by several cranidia. Pygidia have been 

 assigned to it but are not illustrated because of uncertain relationship. 



