NO. 8 SARDINIAN CAMBRIAN GENUS OLENOPSIS 243 



about 250 feet below the top of the Lower Cambrian in gray siliceous 

 shale (102 feet) forming 5 of Mount Whyte formation, Mount 

 Stephen Section, just above the tunnel, north shoulder of Mount 

 Stephen, 3 miles east of Field, British Columbia; all in Canada. 



OLENOPSIS AMERICANUS, new species 



Plate 36, tigs. 8- 1 1 



Olenopsis ? sp., Walcott, 1908, Smithsonian Misc. Coll., Vol. 53, No. 5, p. 

 202. (Mention of genus in list of fossils from Gordon Mountain.) 



This species is a rare form and is known only by a few fragments 

 of the dorsal shield and several specimens of the cranidium. Its 

 locality has been thoroughly worked on two occasions without 

 securing entire specimens. 



The cephalon as restored by uniting the cranidium and free cheeks, 

 has a transverse, semicircular outline with rather strong spines at 

 the genal angles. Marginal border rather broad, slightly flattened, 

 and uniting at the genal angles with the well-defined, rounded 

 posterior border. In front of the glabella the inner margin of the 

 border curves gently backward, narrowing the frontal limb. 



Glabella subconical and marked by three pairs of glabellar furrows, 

 the anterior of which are shallow and often obscure. A shallow fur- 

 row connects the inner ends of the slightly oblique posterior pair. Oc- 

 cipital ring strong and separated from the glabella by a narrow, shal- 

 low occipital furrow. Dorsal furrow about glabella very distinct. 

 Fixed cheeks broad, large, and merging posteriorly into large postero- 

 lateral limbs, and anteriorly into the narrow frontal limb. Palpebral 

 lobes of medium size ; a strong, narrow ridge extends from the front 

 end of each lobe across the fixed cheeks to the dorsal furrow opposite 

 the second lobe of the glabella. Free cheek large and rising rapidly 

 from the margin to the base of the medium-sized eye. 



A portion of the thorax showing 16 segments indicates that the 

 pleural lobes were about twice as wide as the axial lobe and the 

 pleural furrow of each segment long, strongly impressed, and 

 extending from the inner anterior margin out to the falcate extremity 

 of the pleura. 



Pygidium unknown. 



Surface formed of a fine irregular network of elevated, very 

 narrow ridges, suggestive of the reticulated surface of the Mesona- 

 cidae. 



Observations. — This was the first species of this genus discovered 

 and identified in America. I put the specimen aside in 1905 with 



