256 Proceedings oj the Royal Society of Victoria. 



3. Dorsal line terminating posteriorly in a distinct angle, 



margin thence declining obliquely ; front deep and 

 boldly curved, umbones very large and prominent, 

 ridges about 12, equidistant; sculpture reticulate near 

 the margin, becoming irregularly hexagonal more dis- 

 tally. Head in lateral view with upper distal 

 extremity produced hindwards a little, forming an 

 acute angle with the apex rounded off; very prominent 

 in front of eyes. Tail possessing very few irregularly 

 placed little denticles. — sarsii. 



4. Shell large, long, and tumid, back straight for almost its 



total length, umbones very small and quite near the 

 anterior limit, ridges equidistant, 12-16, sculpture irregu- 

 larly reticulate. Head in lateral view sharply bent at 

 a right angle and projecting considerably beyond the 

 level of the cervical segment ; a little prominent in 

 front of the confluent eyes. Tail-piece with dorsal 

 denticles small, few (about 5), only one comparatively 

 short pair in front of anal setae. — lutraria. 



5. Lateral outline of shell quite similar to above, but more 



compressed, of thinner consistency and smaller size : 

 ridges equidistant, about 10, sculpture well defined irreg- 

 ularly hexagonal spaces. Eyes separated by a narrow 

 space. Tail-piece bearing about eight long slender den- 

 ticles, one pair in front of anal setae very long, slender, 

 curved hindwards. Caudal claws with none or very few 

 feathered setae at the base. — dictyon. 



Genus— Cyclesthepia, G. 0. Sars, 1887. 

 Cyclestheria hislopi (liai.d). (PI. XXXVL, Fig. C 1, 2). 



Estheria hislopi, Baird. Proc. Roy. Soc. London, xxlvii. 

 (1859), pi. Ixiii., fig. 1. 



Limnadia hislopi, Brady. Journal Linn. Soc, xix., p. 294, pi. 

 xxxvii., figs. 1-3. 



Cyclestheria hislopi, Sars. Vid. Selsk. For., Christiania, 1888, 

 No. 1, jip. 6-60, pis. i-viii. 



Shell somewhat tumid, with the valves rather thin and pellucid, 

 irregularly rounded, dorsal line in adult females very strongly 



