38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL.98 



pletely above the fixigenes, rising on the sides rather rapidly reaching 

 the greatest curvature near the median line but without producing a 

 keel. The fixigenes are convex, sloping down rather rapidly to a broad 

 palpebral furrow. The wide eye band rises from the furrow. The 

 eyes are of moderate length, extending from the front glabellar 

 furrow to a point forward of the occipital furrow. Anterior to the 

 eyes the fixigenes form a small flange which joins the narrow brim. 

 The brim consists of a narrow rim, slightly upturned. Surface finely 

 granulose. 



Locality 54s. 



Holotype.— U.S.N.M. No. 98514. 



PTARMIGANIA EXIGUA, n. sp. 



Plate 4, figs. 1-10 



This is a common species, being represented by one cephalon, many 

 cranidia, libragenes, and pygidia. 



The glabella is long, expanding forward from the occipital furrow 

 at an even rate to rounded anterior angles. The usual sets of furrows 

 are deeply impressed. In cross section the species is convex, and the 

 evenly arched glabella is above the dorsal furrow. The fixigenes are 

 only slightly convex and have a horizontal position. Longitudinally 

 the cranidium is very convex. The palpebral lobe, which is the fixi- 

 gene, is about two-thirds the width of the glabella at that point. The 

 occipital spine is stout and long, and the posterolateral limbs are long. 

 The eyes extend from a little forward of the posterolateral limbs to 

 the third pair of glabellar furrows and are set at a considerable angle 

 to the dorsal furrow. The eye band is wide and slightly upturned. 

 Eye lines strong. Anterior fixigene fairly wide and turned down at 

 the outer angles. Brim simple, convex with the anterior margin 

 strongly striated. Fixigene, attached to the holotype, highly convex 

 and placed almost vertical to the palpebral lobe. Outer edge striated 

 to correspond to rim and increasingly upturned toward the front. 

 Genal spines long. 



The pygidium is characterized by a stout axis in which two rings 

 and a large terminal segment are defined, the anterior ring carrying 

 a large spine. Three pleura visible on the platforms, but on the wide 

 border four may be discerned. Each pleuron extends into a short 

 blunt marginal spine. 



Surface of the entire test granulose with the granules fairly evenly 

 distributed except in the furrows. 



Locality 54s. 



Holotype and paratypes. — U.S.N.M. Nos. 985153^. 



