28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



The brim is simple and narrower than in most species. The 

 associated hypostoma is illustrated in figure 18, together with another 

 cranidium. The pygidium assigned to the species is not completely 

 fused, as two segments are traceable, beside furrows on the third. 

 The marginal spines are three in number. The pygidium is further 

 characterized by a rather strong post-axial ridge and by the straight 

 lateral margins. 



P. decorosus is much like P. alatus in the large size of the eyes. 

 It is distinguished quite readily by the more even curvature of the 

 eye lobes. 



Locality 54s. 



Holotype and paratypcs. — U.S.N.M. Nos. o,8495a-c. 



PROZACANTHOIDES EXILIS, n. sp. 

 Plate 3, figs. 19, 20 



This species is represented by a considerable number of specimens. 

 It is characterized by a rather broad glabella on which the furrows are 

 indicated by faint depressions. The glabella is slightly keeled. The 

 occipital furrow is considerably reduced, consisting of two deep 

 elongated pits connected across the middle by a shallow furrow. The 

 palpebral lobes at their greatest width equal exactly half the 

 glabellar width. The eye bands are particularly wide, the eyes are 

 rather evenly curved and set at a smaller angle to the dorsal furrow 

 than in any other species. The brim is wide. The pygidium assigned 

 to the species is narrow with a wide axis well fused with only one 

 segment traceable. The axis is prominent because of its large size 

 and because the narrow pleural lobes are slightly concave, rising 

 from the dorsal furrow. The pygidium has a very small spine on the 

 first segment. The surface is covered by fine anastomosing lines. 



Locality 54s. 



Holotype and paratype. — U.S.N.M. Nos. 98496a, b. 



PROZACANTHOIDES AEQUUS, n. sp. 



Plate 3, figs. 21-23 



This species is represented by a number of cranidia, to which one 

 pygidium had been assigned. It is characterized by low relief and a 

 high degree of fusion. Several of the glabellar furrows are indicated 

 by wide shallow depressions ; likewise the occipital furrow. The 

 widened neck ring is peculiarly marked by irregular striations 

 radiated from the short occipital spine and covering the latter 

 half of the ring. At their widest point the palpebral lobes are a little 



