NO. 6 MIDDLE CAMBRIAN BRANCHIOPODA, ETC. 20I 



edge of the cephalic shield; these terminate in a minute joint having 

 several fine setfe or spines on its margin. 



On the thoracic leg two or three of the inner joints are widened 

 out and setiferous ; the outer three joints are long and slender ; on the 

 outer side of the inner joints (exopodite probabl}^) there is a broad 

 flabellum-like setiferous lobe, also a small oval gill (fig. 3). From 

 beneath the posterior margin of the long abdominal segment shown in 

 figure 4, a minute jointed leg projects on each side of the base of the 

 telson. 



Inferior structure. — The alimentary canal is outlined in several 

 specimens. On one of them (fig. 2) it extends to the posterior end 

 of the long abdominal segment, thus indicating the position of the 

 anal opening. Traces of the hepatic caeca beneath the head are 

 shown by figure 3. 



Dimettsions. — This is a small species. The largest specimen has 

 a length, exclusive of the telson, of 40 mm. The average length is 

 about 18 to 20 mm. The proportions of the dorsal shield and telson 

 are indicated by figure 2. 



Observations. — I have employed above the terminology used in 

 describing the dorsal shield of trilobites as it applies so well to this 

 interesting species. In outward aspect the dorsal shield is essentially 

 that of a trilobite except that there are no sessile eyes on the head 

 shield and the posterior segments are more nearly related in form to 

 such branchiopod crustaceans as Emeraldella brocki (pi. 30, fig. 2). 



So far as can be determined, a pair of jointed legs, with an exopo- 

 dite bearing a gill and flabellum, occurs on the outer side of each of 

 the eight thoracic segments. A moderate number of specimens of the 

 species were found in 1910 and it may be that more will be collected 

 during the season of 1912 and that among them the cephalic append- 

 ages will be preserved. The test is thin and easily wrinkled, which 

 obscures parts that would otherwise show through 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. 



HABELIA, new genus 



The description of the genus is included with that of the type 

 species. 



Genotype. — Habelia optata, new species. 



Stratigraphic range. — The stratigraphic range is limited to a layer 

 in a band of dark siliceous shale about 4 feet in thickness, forming 

 a part of the Burgess shale member of the Stephen formation. 



