26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



Numerous well-preserved specimens permit close specific dis- 

 crimination, which shows that this form is P. clytia, characteristic of 

 the overlying Spence shale. 



Locality 54s. 



Plesiotypcs. — U.S.N.M. Nos. 984923-1!. 



ZACANTHOIDEA Swinnerton 

 PROZACANTHOIDES Resser, 1937 



This genus is represented hy five species in the collections from 

 locality 54s and one from locality 59f, near Liberty. Unidentified 

 species occur in the Langston of Blacksmith Fork. This represents 

 a great expansion for the genus, and most of the species are repre- 

 sented by many specimens. 



As the species are here set up heads and tails have been matched 

 according to shape and surface ornamentation. One specimen retains 

 the libragenes and part of the thorax. 



Considerable similarity exists between the cranidia of Prozacan- 

 thoides and Dolichometopsis and Plarmigania, and the pygidia of 

 Prozacanthoides are sometimes difficult to tell from those of Ko- 

 chaspis and even of Kochiella. Similar likenesses are observed among 

 the hypostomata. In several respects Prozacanthoides lies between 

 Zacanthoides and Albertella. 



PROZACANTHOIDES ALATUS, n. sp. 



Plate 3, figs. 10-12 



This species is represented by several cranidia and pygidia, which 

 have been selected on the basis of surface ornamentation and degree 

 of fusion. The glabella is parallel-sided and rounded at the anterior 

 angles, with a flattened curvature in front. The occipital furrow is 

 straight and clearly defined but not deep. The occipital ring has a 

 fairly large spine. Four pairs of glabellar furrows are faintly indi- 

 cated. The fixigenes are confined to the palpebral lobes and at their 

 widest point are a little more than half the width of the glabella. 

 The eyes are very long, and the eye band is wide. The eyes extend 

 from the anterior angles of the glabella outward at a considerable 

 angle, with a nearly straight outline for about two-thirds their length. 

 In the rear third the curvature increases very rapidly, and the rear 

 portion of the eye lobe evidently overhangs the occipital furrow. The 

 brim is simple without a rim, slightly concave, and upturned. The 

 facial suture diverges at about the normal rate. 



