SuTER. — On New Zealand MoUusca. 289 



median line of the radula. To the straight side of the median 

 cusp a sharp, rather stout cutting-point is fastened. The 

 outer cusp bears a short cutting-point. 



Marginals not much broader than long, the anterior part 

 rhomboidal, the inner ones with three, the outer ones some- 

 times with four teeth, of wliich the second on the inner side 

 is the strongest. Last marginals with rudimentary teeth, 

 minute. 



Amphidoxa chiron, Gray. From Ohaupo, North Island. 

 Plate XX., figs. 10, a, h, 11, 12. 



Jaio arcuate, membranaceous, vertically plaited with 

 about fifteen rather broad flat plaits, w^hich are separated by 

 narrow grooves. Upper margin smooth, cutting - margin 

 slightly denticulated, and with a blunt median projection. 

 A transverse striation runs from one end to the other. 



Badiila tongue-shaped, consisting of about 110 straight 

 transverse rows of teeth, 12—5 — 1 — 5 — 12. 



Central tooth rectangular, longer than broad, anterior end 

 curved, reflection rather large, tricuspid ; middle cusp long, 

 with the short cutting-point reaching near the posterior end 

 of the base ; side-cusps slightly sinuated on the outer sides, 

 cutting-points small. 



Laterals asymmetrical, rectangular, somewhat larger than 

 the central ; reflection large, irregularly shaped, tricuspid, the 

 median cusp in the outer teeth extending to the posterior end 

 of the base, its cutting-point well developed, running partly 

 over the next row of teeth ; the inner side cutting-point attain- 

 ing by degrees a greater development than the outer one, 

 which remains small. 



The first marginal tooth, together with the last lateral, 

 may be considered as transition teeth ; the other marginals 

 broader than long, tridentate, the middle tooth broad, short, 

 the inner one longer and narrower, the outer one short. 

 From the 14th to the 16th tooth the denticles coalesce by 

 degrees into one mass ; the last rudimentary. 



The specimens from Ohaupo, collected by Mr. Charles T. 

 Musson, and of which 1 give a figure, are so strongly plaited 

 that I first took them for a new sjDecies, closely allied to 

 A. chiron; but the dentition is decidedly that of the species 

 mentioned, as described and figured by Professor F. W. 

 Hutton in Trans. N.Z. Inst., vol. xvi. This species seems to 

 vary very much with regard to the plaits. Specimens I col- 

 lected in the Forty-mile Bush show almost no trace of plaits, 

 but only well-developed growth-lines. The shells from Ohaupo 

 correspond with Gray's description, though I should not call 

 them plaited, but ribbed. 



A. chiron may be considered as an intermediate form 

 19 



