44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



about the usual proportions and stands above the pleural lobes. Both 

 the pleural furrows and pleural grooves are deep ; the anterior ones 

 extending to the margin and those near the rear end of the axis ending 

 abruptly some distance from the margin. The pleural platforms are 

 small and the outer edges are upturned, so that the entire pygidium 

 appears concave. 



Locality 59c. 



Holotypc and paratypes. — U.S.N. M. Nos. 98527a-d. 



ORYCTOCEPHALIDAE Beecher 

 ORYCTOCEPHALITES, n. gen. 



Small trilobites related to Oryctocephalus. The glabella is long, 

 extending the full length of the cranidium, expanding forward. The 

 occipital furrow is deeply impressed and three pairs of glabellar 

 furrows are present. None of them reach to the dorsal furrow. The 

 rear pair consists of two elongated pits connected by a shallow furrow 

 across the median line, while the forward pairs consist merely of 

 elongated pits. The dorsal furrow is deep. The fixigenes average less 

 than half the width of the glabella. The eyes are large, extending 

 from the occipital furrow forward a little more than half the length 

 of the glabella and are set at a considerable angle to the course of 

 the dorsal furrow. Weak eye lines connect their anterior ends with 

 the dorsal furrow. These eye lines pass forward parallel to the 

 strongly curved anterior margin, reaching the glabella forward of 

 the anterior pair of furrows. The brim is confined to a narrow up- 

 turned rim. The pygidium is well fused in the anterior portion. Its 

 axis is rather prominent, contracting rather rapidly toward the rear 

 and extending somewhat more than two-thirds the length of the 

 pygidium. Four axial rings and a terminal segment are delimited. 

 The pleural grooves are deep, and the pleural furrows are traceable, 

 becoming better defined toward the rear so that the segmentation of 

 the rear portion of the pygidium can be clearly traced. Five pairs of 

 marginal furrows are present, and these increase in size from the 

 anterior angles to the fourth spine, which is very large, while the fifth 

 is reduced to small, slender points. A wide, flat, postaxial ridge 

 extends to the rear margin. 



This genus differs from Oryctocephalus in the expanded glabella, 

 which extends forward beyond the fixigenes, at the anterior angles, 

 the reduction of the forward glabellar furrows to pits, the lesser 

 development of the eye line, and the more posterior position of the 

 eyes. In the pygidium the difference is expressed by a greater degree 



