314 Firderich CJiopmaii : 



(?) Sreiitlla raridiis,^ a species from the Middle Cambrian of the 

 United States and Canada, resembling our fossil in some 

 particulars. TTie related genus Stenotheca occurs in the Cam- 

 brian of South Australia, and is distinguished from the above 

 genus by its stronger, rugose shell and curved beak. The latter 

 feature is not emphasised to any degree in oiir specimen, and 

 the smoother shell shows it to be distinct from Steiwtlieca in 

 that respect. 



Horizon. — Upjjer Cambrian. Agnostus Zone. Dolodrook 

 Rivei'. 



Class Crustacea. 



Sub-class TriJohita. 



Genus Af/iinsfu'<, Brongniart, 1822. 



Agnostus australiensis, sp. nov. 

 (PI. LVITI., Figs. 9, 11. 12). 



Description. — Head subquadrate. margin narrow. Glabella 

 conical, narrow, bilobed ; anterior lobe small, pointed in front, 

 half as long as the posterior ; posterior lobe wider and sub- 

 rectangular ; basal lobes snlall, sub-triangular. Cheeks elevated, 

 surface dull, relieved by very faint radial striae ; not so elevated 

 as glabella, and of nearly equal width except in region of an- 

 terior glabellar lobe, where they are wider. 



Thorax not well preserved in our specimens ; portions of 

 lateral and axial elements somewhat crushed, but apparently 

 rather wide. 



Tail broad, sub-circular, with a narrow margin produced into 

 short spines at the posterior angles ; axis moderately wide, an- 

 terior segment narrow, almost bilobed by the intrusion of the 

 middle segment which is anteriorly produced and bearing a 

 strong central tubercle : posterior segment large, elliptical or 

 guttate, being produced behind into a blunt point. Lateral 

 lobes of uniform width, except where confluent behind the pos- 



1 Op. clt, p. 127, pi. xii., fitr.s. 2, 



