62 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



TAXIOURA, n. gen. 



A very abundant trilobite with a large tail forms a conspicuous 

 element of the fauna. Its description has been delayed by its reference 

 to Ogygopsis. 



The cranidium is characterized by clear definitions of the usual 

 parts, all, however, developed on a simple pattern. The glabella is 

 large, rectangular in shape except for rounding at the anterior corner, 

 and occupying nearly the full length of the cranidium. Glabellar 

 furrows are very faint. Brim narrow, concave, and without a rim, 

 except as differentiated by an upturning of the outer margin. Eye 

 lines conspicuous. Fixigenes roughly the same width throughout 

 from the anterior angle to the rear end of the eye. Posterolateral 

 limbs of normal size and shape. Eyes of moderate size and situated 

 about the midpoint of the cranidium. Libragene of normal composi- 

 tion, evidently sloping down rather sharply from the eye lobe and 

 with a well-demarcated border. The moderately long genal spines 

 have a peculiar shape. The posterolateral limbs do not reach the genal 

 angle but a flange equal to their width is formed as a connection by 

 extension from the ocular platform. Surface covered with fine 

 anastomosing lines on the ocular platform, changing to striations on 

 the border. . 

 , Pygidium approximately semicircular. Axis narrow and occupying 

 the full length of the pygidium, differentiated into about 10 rings 

 and the terminal segment, which extends into a postaxial ridge. 

 Pleural lobes large, well fused. Pleural furrows conspicuous and 

 straight. Pleural grooves obsolete. Margin smooth except for a 

 small recurved spine at the anterior corner and an indentation at the 

 rear of the axis. 



Hypostoma not located. 



Name. — ra£is = regularity; oi^a = tail. 



TAXIOURA TYPICALIS, n. sp. 



Plate 14, figs. 6-14 



This species is very abundant, the separated shields often forming 

 almost the entire rock. The glabella is long and simple, tapering 

 slightly both forward and rearward and is slightly protuberant in 

 front. Glabellar furrows only faintly seen in direct longitudinal 

 light. In cross section the glabella rises with a flat curve only 

 moderately above the dorsal furrow and in longitudinal section has a 



