72 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 148 



posterior pair very oblique, moderately deep ; third pair shorter and 

 shallower, directed slightly backward; second pair very short and 

 shallow, directed slightly forward. Occipital furrow deep, occipital ring 

 bearing a node. Preglabellar field slightly convex longitudinally and 

 more or less downsloping in different individuals. Border furrow well 

 impressed, in some cranidia showing an indication of the median angle 

 more marked in several other species of the genus. Border somewhat 

 convex, not greatly tapered laterally ; midlength (sag.) of border about 

 half the length of preglabellar field. In anterior view the border appears 

 fairly arched transversely in some cranidia, especially the larger ones, 

 rather flat in smaller individuals. It was considered whether this might 

 be a specific distinction ; however, since the two kinds are mixed in the 

 collections from both localities where the species was found, it was 

 thought more likely that the differences are due either to growth 

 stages, to intraspecific variability, or both. Palpebral area somewhat 

 convex, on average horizontal, half as wide as glabella. Ocular ridges 

 straight, slanted backward, more strongly so in the larger cranidia. 

 Palpebral lobe defined by deep furrow even on upper surface, narrow, 

 strongly curved, somewhat convex transversely, 0.20 to 0.25 times as 

 long as glabella; distance from posterior margin greater than length 

 of lobe. Anterior section of facial suture as divergent as in an average 

 Aphelaspis. Posterior area slender, somewhat narrower (tr.) than 

 occipital ring. Ocular platform moderately convex. Border on free 

 cheek of uniform width, almost flat, defined by shallow furrow ; genal 

 spine strong, of moderate length. 



All portions of the cranidial surface except in the furrows covered 

 with granules, usually of two sizes, although in some of the cranidia 

 only the larger granules are distinct. The border of the free cheek has, 

 in addition to dense, fine granules, a few scattered, somewhat larger 

 granules. Length of largest (holotype) cranidium 15 mm. 



Pygidium twice as wide as long. Axis large, wider than the pleural 

 lobe, elevated, subcylindrical, rounded at the extremity, extended into 

 a short postaxial ridge reaching the posterior margin. First two axial 

 rings well defined, the rest merging into a terminal section. Pleural 

 platforms without much relief, with 2 pairs of broad, rather indefinite 

 furrows. Border rather narrow, flat, poorly defined. In posterior view 

 the posterior margin appears elevated medially. Surface finely granu- 

 late. 



Discussion. — The cranidium seems definitely referable to Dunder- 

 bergia and shows most similarity to D. bigranulosa Palmer (1960) 

 and D. anytus (Hall and Whitfield), both from Nevada. The pygidium 

 also closely agrees with pygidia of Dunderhergia figured by Palmer. 

 D. bigranulosa is from the Dunderbergia zone, while the stratigraphic 

 position of D. anytus, does not seem to be known with certainty. 



