170 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



OPABINIA ? MEDIA, new species 



This species was not recognized until after the plates illustrating 

 the crustaceans from the Burgess shale had been completed. 



It differs from Opabinia regalis (pi. 27, fig. 6) (a) in being much 

 smaller, (b) in having a proportionately smaller head, and (c) in 

 having fewer segments, 12 or 14. The frontal appendage is not 

 clearly shown, but it is small compared with that of O. regalis. 



The appendages of the thorax have an expanded setiferous ter- 

 minal joint, and there are traces of a small, broad, lanceolate gill or 

 flabellum toward the basal part of the leg. 



The two largest specimens each have a length of about 38 mm. 

 The specimens of this species are not well preserved, but the char- 

 acters are sufficiently clear to distinguish the species from O. regalis 

 A thorough search will be made for better specimens during the 

 season of 1912. 



Formation and locality.— Middle Cambrian : l^^-) Burgess shale 



member of the Stephen formation (about 75 feet above the phyllop.od 

 bed near the base of the shale) on the west slope of the ridge be- 

 tween Mount Field and Wapta Peak, one mile (1.6 km.) northeast 

 of Burgess Pass, above Field, British Columbia. 



LEANCHOILIA, new genus 



The generic description is included with that of the type species. 



Genotype. — Leanchoilia siiperlata, new species. 



Stratigraphic range. — The stratigraphic range is limited to a band 

 of dark siliceous shale about 4 feet in thickness forming a part of 

 the Burgess shale member of the Stephen formation. 



Geographic distribution. — On the slope of the ridge between 

 Wapta Peak and Mount Field, north of Burgess Pass, and about 

 3800 feet above Field, on the line of the Canadian Pacific Railway, 

 British Columbia, Canada. 



The generic name is derived from Leanchoil, the name of a rail- 

 way station on the Canadian Pacific Railway, 17 miles southwest of 

 Field, British Columbia, Canada. 



LEANCHOILIA SUPERLATA, new species 



Plate 31, fig. 6 (lower specimen) 



Body elongate, with clearly defined head shield and nine strong 



body segments up to the point where the posterior part of the body 



is broken off. The anterior pointed end of the head is broken off 



in such a manner that the presence of a frontal appendage is sug- 



