340 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



The largest cranidium has a length of 19 mm. and the largest 

 pygidium has a length of 22 mm. and a width of yj mm. 



There are six cranidia and six pygidia in the collection at locality 

 4w that were associated in the same thiri layer of sandstone. The 

 associated fossils are Wimanella simplex, Ptychoparia sp. undt., and 

 Zacanthoides sp. undt. As the two latter do not have a pygidium of 

 the Bathyuriscits type, I think we are fairly safe in tentatively con- 

 sidering the pygidia as belonging with the cranidia referred to 

 Bathyttriscus. 



An associated hypostoma of the Bathyuriscus form has the surface 

 of its central portion marked by line, sharp, irregularly concentric 

 ridges. None of the cranidia or pygidia appear to have the outer 

 surface of the test. They occur as casts in a very fine, chocolate- 

 colored, arenaceous shale. 



Formation and locality. — Lower ? Cambrian: (4w) About 315 

 feet (96 m.) above the unconformable base of the Cambrian and 190 

 feet (57.9 m.) above the top of the quartzitic sandstones in a shale 

 which corresponds in position to shale No. 6 of the Dearborn River 

 section,^ on Youngs Creek, about 5 miles (8 km.) from its junction 

 with Danaher Creek; and (8j) about 575 feet (175.3 ^■) above the 

 unconformable base of the Cambrian in a shale which corresponds in 

 position to shale No. 4 of the Dearborn River section," on the ridge 

 betweexi Gordon and Youngs Creeks, about halfway between Gordon 

 Mountain and Cardinal Peak ; both in Ovando quadrangle (U. S. 

 G. S.), Powell County, Montana. 



BATHYURISCUS ? BITHUS, new species 

 Plate 47, figs. 4, 4a 



This species is based on two pygidia that indicate a form larger 

 than any known species of Bathyuriscus, in this respect approaching 

 Dolichometopns tontoensis (pi. 51, figs, i, if, ig). The axial lobe 

 has six indicated segments and a terminal section, the segments 

 extending obliquely backward on the pleural lobes and nearly across 

 the broad, flattened margin. 



Surface slightly roughened by fine, irregular, inosculating ridges 

 that on the border are subparallel to the outer margin. 



The larger pygidium has a portion of a thoracic segment attached 

 to it. It has a length of 33 mm. The smaller pygidium is 20 mm. 

 in length. 



^ Smithsonian Misc. Coll.. Vol. 53, No. 5, 1908, Walcott, Cambrian sections of 

 the Cordilleran area, p. 202. 



