NO. 6 MIDDLE CAMBRIAN BRANCHIOPODA, ETC. 2O3 



not noted until too late to illustrate it thoroughly. This will now be 

 left until a further study can be made of it. 



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

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

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

 of Burgess Pass, above Field, British Columbia. 



EMERALDELLA, new genus 



The description of this genus is outlined in the description of the 

 type species. 



Genotype. — Emeraldella brocki, new species. 



Strati graphic 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. 



Observations. — -This genus appears to come within the limits of 

 the family Aglaspidge. 



The generic name is derived from the name Emerald as applied to 

 a mountain, lake, and glacier north of Burgess Pass, British Colum- 

 bia, Canada. 



EMERALDELLA BROCKI, new species 

 Text figure 8, p. 204, and plate 30, fig. 2 



Body elongate, strong. As flattened in the shale it is about twice 

 as long as its greatest diameter. Cephalon transversely semicircu- 

 lar. Eyes unknown. Thorax with ten segments bearing appendages. 

 Abdomen with two long anterior segments and a short segment to 

 which is joined a long, slender spine-like telson. Epistoma elongate 

 and a little more than one-half the length of the cephalon. 



Appendages. — The base of an antenna is fairly well shown by a 

 specimen in which the head has been largely broken away (a', fig. 2, 

 pi. 30). It has a thick, jointed basal portion. The two slender, jointed 

 appendages projecting below the head on figure 2 may be the out- 

 ward extensions of the maxillula (mx') and maxilla (mx"). 



A specimen found in 191 1 shows a short antennule (text figiare 

 8), very long slender antennae, and three cephalic appendages. 



The thoracic limbs are not well preserved, but what is shown indi- 

 cates a broad, large terminal joint somewhat similar to that of 

 Opabinia regalis (pi. 27, fig. 6) and another inner joint that is ex- 

 panded and provided about its margin with strong setae. The gill 

 appears to be present but it cannot be satisfactorily determined. 



