NO. 5 MIDDLE CAMBRIAN ANNELIDS 133 



Compared with recent annelids Oesia resembles some of the 

 Maldanidse/ In the absence of the details of head structure, setae, 

 etc., it is not practicable to compare the genera, although Nicomache 

 japonica' looks as though it might appear very much like Oesia 

 disjuncta if it were flattened out on a smooth surface. 



Genotype. — Oesia disjmicta, 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. 



Generic name derived from Oesa, name of a lake east of Lake 

 O'Hara, British Columbia, Canada. 



OESIA DISJUNCTA, new species 



Plate 20, figs. 3-5 



All this is known of this species is illustrated by the figures on PI. 

 20. It appears to have been a form that lived in an irregular tube 

 that was so thin the annelid shows through it. The segmentation 

 is shown by fig. 3, and the enteric canal in the three specimens illus- 

 trated and several others in the collection. The variation in ap- 

 pearance is very great. No two specimens are alike. Traces, of 

 minute hooks at the anterior end have been observed on one speci- 

 men. 



The largest specimen has a length of 10 cm., with a relativelv 

 small head. 



Formation and locality. — Middle Cambrian: (35k) Burgess shale 

 member of the Stephen formation, west slope of ridge between 

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

 Burgess Pass, above Field on the Canadian Pacific Railway, British 

 Columbia, Canada. 



^ Challenger Rept. Zool., Vol. 12, 1885, pis. 46 and 47. 

 * Idem, pi. 46, fig. 5. 



