184 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



extending" beyond the carapace. The terminal segment has from two 

 (fig. 4) to six (fig. 5) cercopods attached to it. 



A strong adductor muscle scar (adm, figs, i and 2) is shown on 

 many specimens. 



A pair of small pedunculated eyes project in front of the carapace, 

 one showing on each side of a pair of minute antennules. 



Appendages. — Head. Several specimens show a pair of minute, 

 jointed antennules projecting forward from between the large jointed 

 antennas (fig. 2). The antennae are large and are composed of a 

 single stem of short joints ; they may, however, be straight, unjointed, 

 and long (fig. 2, pi. 31). I have not illustrated a specimen showing 

 the antennules and eyes, as they were not observed until after the 

 plates were made up. 



The specimen illustrating the thoracic legs and head appendages 

 (fig. i) is unfortunately not so good as one which was found and 

 cleaned of calcareous deposits after the plates were finished and before 

 this description was written. This specimen shows three cephalic 

 legs. The two anterior are slender (mandible and maxillula), and 

 the posterior maxilla is large and formed of short strong joints. 

 There are eight pairs of thoracic legs. The distal portions of these 

 are finely shown in figure i. The broad, setiferous joints of the 

 exopodite are also shown near the carapace. In other specimens they 

 extend out over the legs so as nearly to conceal them. Traces of 

 oval gills (epipodites) are shown for three legs on the outer side of 

 what appears to be the second joint of the leg. 



Interior structure. — The alimentary canal may be traced from the 

 anterior part of the body back to the posterior abdominal segment 

 where it terminates between two larger cercopods of the type repre- 

 sented by figures i and 2. One specimen, not illustrated, appears to 

 have a considerable enlargement of the canal in the head portion. 



Dimensions. — The valves of the carapace average from 40 to 60 

 mm. in length, with other proportions as shown by figure i. 



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

 through about 25 feet of the 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. 



HYMENOCARIS ? CIRCULARIS, new species 



Plate z^, fig- 4 

 This is a much smaller species than the other species of this genus 

 from the Burgess shale and I am not sure that it should be referred 



i 



