SuTEit. — 0)1 Ncio Zealand Mollusca. 291 



of teeth. The other marginals get much broader than long, 

 and are provided with three or four denticles, which in the last 

 teeth are more or less coalescing, with the denticles blunt. 



Therasia decidua, Pf. From Hooker Valley, South Island. 



Plate XXI., figs. 16, 17. 



Jaw membranaceous, horseshoe-shaped, with imbricating 

 plaits, which are very broad in the centre, narrower towards 

 the ends ; they nearly reach to the upper margin, but are 

 rather distant from the cutting-margin, which has a pro- 

 nounced median projection. 



Badiila long, tongue-shaped, consisting of about 150 trans- 

 verse almost straight rows of teeth, 29 — 8 — 1 — 8 — 29. 



Central tooth rectangular, long and narrow. Eeflection 

 small, side-cusps hardly visible, with one median cutting-point 

 only, reaching nearly to the posterior margin of the base. 



Laterals with a broader base, reflection larger, the inner 

 teeth with one cutting-point only, three on the outer ones. 

 The median cutting-point stout, long, extending almost to the 

 posterior margin, the side cutting-points small. 



Marginals first bicuspid, then tricuspid, rounded at the 

 anterior margin. On the outer marginals the cutting-points 

 coalesce in one, which is trifid. The last two or three are 

 bidentate. 



Psyra tullia, Gray. From Sealev Eange, South Island. Plate 



XXI., figs. 18, 19. 



Jaio slightly arcuate, not tapering, with about 14 flat broad 

 plaits slightly indenting both margins. 



Badula consisting of about 80 transverse straight rows of 

 teeth, 15—6—1—6—15. 



Central tooth rectangular, somewdaat longer than broad. 

 Eeflection tricuspid, median cusp slender and reaching with 

 its short cutting-point over three-quarters of the length of the 

 base. Side-cusps rounded, short, each with a minute cutting- 

 point. 



Laterals highly asymmetrical, base rectangular, much 

 longer than broad. Eeflection bicuspid, the internal cusp 

 bearing a strong cutting-point, reaching to the posterior 

 margin of the base ; the external cusp rather broad, with a 

 short cutting-point. 



Marginals. — The first two tridentate, resembling somewhat 

 the last laterals, the internal cutting-point being the longest, 

 the anterior portion nearly quadrate. The following teeth get 

 gradually broader, and of the three well-developed cutting- 

 points the median is the longest. The last marginals are 

 small, bidentate. 



