236 



figured (probably diagrammatically) by Joan for 0. hovis 

 (Argentine material), and exactly like that indicated by 

 Neumann (1910, p. 275) for 0. gutturosa. The arrangement 

 of the ridges varies, then, according to the position from 

 which they are viewed. 



Figs. 23 to 27, views of side of females (optical section) to 

 show thickness of cuticle, height of ridges, striae, etc. ; all figs, 

 drawn to scale indicated in fig. 28. 23, 0. fasciata (diameter of 

 body at place figured, "41 mm.). 24, 0. gibsoni ("50 mm.). 25, 

 0. gutturosa (-230 mm.). 26, 0. gutturosa (120 mm.). 27, 0. 

 lienalis ('20 mm.); r, ridges. 



