244 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



the hope that better material might be found at about the same 

 horizon in British Columbia. Several of the species found in 

 association with Olenopsis americanus occur there in the Mount 

 Whyte formation, notably Acrothele colleni Walcott, Wimanella 

 simplex Walcott, and Alhertella Helena Walcott,^ but no traces of 

 Olenopsis americamis were found. The genus Olenopsis is there 

 represented by Olenopsis f agnesensis described in this paper. 

 Olenopsis americanus differs from that species in having its palpebral 

 lobes near the transverse median line of the cephalon ; its more 

 distinctly defined frontal border that curves slightly backward in 

 front of the glabella; and its narrower frontal limb and, probably, 

 several more segments in the thorax. The differences between 

 Olenopsis americanus and Olenopsis roddyi are so marked that it 

 will suffice to call attention to the figures illustrating them. It has 

 many characters in common with Olenopsis zoppii (Meneghini) but 

 differs in having a larger number of thoracic segments and in surface 

 sculpture as well as minor details. 



Formation and locality. — Lower Cambrian : (4v) shale about 200 

 feet (61 m.) above the uncomformable base of the Cambrian and 75 

 feet (22.9 m.) above the top of the quartzitic sandstones in a shale 

 which corresponds in stratigraphic position to shale No. 6 of the 

 Dearborn River section,"* Gordon Creek, 6 miles (9.6 km.) from the 

 South Fork of Flathead River, Ovando quadrangle (U. S. Geol. 

 Survey), Powell County, Montana. 



OLENOPSIS RODDYI, new species 

 Plate 36, fig. I 



The general form and relative proportions of the cephalon, thorax, 

 and pygidium are shown by the accompanying illustration, which is 

 a reproduction of a photograph of the type specimen of the species. 

 The cephalon and thorax have been shortened by longitudinal com- 

 pression. This has materially affected the glabella by crowding back 

 its frontal lobe so as to give it a quadrangular outline, and the 

 palpebral lobes, too, have been pushed back toward the posterior 

 margin. 



The marginal border of the cephalon is of medium width, slightly 

 rounded, and uniting at the genal angles with the rounded posterior 

 border of the fixed cheeks before merging into a strong, sharp, 

 narrow, rounded, backward-projecting genal spine. 



' Smithsonian Misc. Coll., Vol. 53, No. 2, 1908, pp. 19-22. 

 ' Idem, p. 202. 



