NO. 5 . MIDDLE CAMBRIAN ANNELIDS II3 



the body and quite prominent. The tail is expanded and sHghtly 

 transverse at the posterior margin. 



The enteric canal and traces of other internal organs show quite 

 clearly. In the head (fig. 3) a triangular-shaped area is outlined in 

 front, and back of it a quadrate space. Posterior to^ the latter are 

 two elongate oval spaces ; from the outer side of the left of these 

 three short hooks curve inward ; these were undoubtedly beside the 

 mouth. The enteric canal begins between the bases of the two 

 oval spaces and terminates a little beyond the center of the tail. 

 The anus doubtless existed at this point. A transverse, somewhat 

 irregular line at the base of the oval spaces, indicates a thin septum 

 separating the head and body cavities. 



Dimensions. — The largest specimen has a length of 20 mm. Other 

 proportions are shown by figures 3 and 4, which represent the body 

 flattened on the shale. 



Observations. — The living representatives of this beautiful little 

 annelid are pelagic and very active swimmers ; this fact and its 

 association in the shale with small free swimming phyllopod crus- 

 taceans indicate very clearly that it was active and free swimming. 

 Only three entire specimens were found. 



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.) north- 

 east of Burgess Pass, above Field, British Columbia. 



Class CH^TOPODA 



SUB-CLASS POLYCH^TA 



MISKOA, new order 



Polychgeta with similar segments and parapodia throughout the 

 length of the body ; retractile proboscis ; straight enteric canal. Body 

 not distinctly specialized into sections. 



MISKOID^, new family 



Body elongate, slender ; with numerous uniform segments ; ante- 

 rior end with rows of strong setse about the mouth. Surface of 

 anterior portion with numerous papillse. Parapodia abundant, 

 branched. Proboscis elongate, retractile. Enteric canal straight, 

 with enlargement in anterior portion. 



Observations. — The long retractile proboscis with the mouth at 

 its base (fig. i) suggests the Class Gephyrea as does the large body 



