BY C. HEDLEY. 689 



in the marginals the main cusp is cleft at its summit and an 

 accessory cusp appears at its distal base. 



Genitalia (pi. xli., fig. 27), penis sac large and ovoid • sperma- 

 theca small, cylindrical, without terminal dilatation. 



Geotrochus brumeriensis, Forbes. 



Jaw (pi. xli., fig. 31) boomerang-shaped, central half crossed 

 by about nine weak ribs, which denticulate either margin, ends 

 smooth, angled. 



Radula (pi. xxxviil, fig. 8) tongue-shaped, twice as long as 

 broad ; formula 110 rows of 40 : 7 : 1 : 7 : 40 ; otherwise as in 

 G. boyeri. 



Genitalia (pi. XL., fig. 21), penis sac small, conical ; vas deferens 

 long and contorted ; spermatheca oval on a long peduncle. 



G. louisiadensis, Forbes. 



Jaw (pi. xxxviil, fig. 2) boomerang-shaped, centre crossed by 

 half-a-dozen weak ribs denticulating both margins, ends smooth, 

 rounded. 



Radula (pi. XL., fig 24) tongue-shaped, twice as long as broad ; 

 formula 142 rows of 45 : 9 : 1 : 9 : 45 ; rachidian. smaller than the 

 immediate laterals, square-headed, extending along three-fourths 

 of the basal plate, whose anterior angles are scarcely expanded ; 

 laterals large, square-headed, alate angle of the basal plate scarcely 

 expanded : marginals tricuspid. 



Genitalia (pi. xl., fig. 19), penis sac large, dilated arid contracting 

 suddenly ; spermatheca oval on a large peduncle. 



G. rollsianus, Smith. 



Jaw (pi. xxxviil, fig. 10) thin, arcuate, central quarter crossed 

 by seven very delicate ribs, ends smooth, rounded. 



Radula (pi. xli., fig. 29) strap-shaped ; formula 154 rows of 

 45 : 10 : 1 : 10 : 45 ; rachidian two-thirds the size of the imme- 

 diate laterals, reflection slightly tapering, terminating in a single 

 square-headed cusp, which does not reach the basal margin ; 



