NO. 6 MIDDLE CAMBRIAN BRANCHIOPODA, ETC. 1/7 



dition of the posterior half of the carapace extended back over the 

 thorax. The hepatic caeca and legs are of the same type. Nothing is 

 yet known of the eyes and labrum, and only a suggestion of the 

 cephalic appendages. 



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

 member of the Stephen formation, on the west slope of the ridge 

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

 of Burgess Pass, above Field, British Columbia. 



BURGESSID^, new family 



Carapace forming a dorsal shield ; paired eyes sessile ; body with 

 fourteen pairs of appendages of which five are cephalic, eight thoracic, 

 and one abdominal, as now known ; many segments, thirty or more, in 

 the abdominal (telson) extension of the body. Labrum relatively 

 large and attached to the anterior reflected edge of the carapace. 

 Thoracic appendages leg-like and with small branchial lobes. 



One genus, Burgessia. 



Observations. — Anticipating that there will be many more speci-' 

 mens available for study in the near future, I will not attempt to 

 correlate the Burgessidse with any described faimly of the Notostraca. 

 I suspect that Burgessia bella is the representative of an irregular 

 order that, like the Leptostraca, does not fall strictly within the def- 

 inition of the subclass to which it is referred. 



BURGESSIA, new genus 



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



Genotype. — Burgessia bella, 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. 



The generic name is derived from Burgess, the name of a mountain 

 and pass near the fossil bed from which Burgessia bella was collected, 

 British Columbia, Canada. 



BURGESSIA BELLA, new species 



Plate 27, figs. 1-3, and plate 30, figs. 3 and 4 



Carapace large, semicircular in outline when pressed flat, with a 



rounded notch at the posterior side where the thorax appears from 



beneath the carapace. The test is very thin and it has often been 



3 



