54 Transactions. — Zoology. 



Art. VI.— The Freshwater Shells of New Zealand belonging to the Family 

 Limnseidse. By Professor F. \V. Hutton. 

 [Read before the Philosophical Institute of Canterbury, oth June, 1884.] 

 Plate XII. 

 The New Zealand Limneeida are not very numerous in species although 

 they are usually very variable. Li-mama is rare, or abundant only in a few 

 localities. Aplecea is far more common, but not nearly so abundant as 

 Potamopyrgus. Our single species of Planorbis is so small it may easily be 

 overlooked, but it does not appear to be common. I have to thank Mr. 

 H. M. Gwatkin for sending me odontophores of the British Limnceidce 

 without which I should have hesitated to name some of our species. 

 Limn^ea (Amphipeplea) arguta, sp. nov. PL xii., fig. 1. 

 Shell globosely ovate, glossy horn brown when dry, dark olive green 

 when alive ; rather strongly longitudinally striated, and without any spiral 

 lines. Whorls 3 or 3|, the last inflated, spire very short, slightly acute, 

 usually eroded at the apex, suture moderate, simple. Aperture large, ovate, 

 occupying three quarters of the entire length of the shell ; columella 

 arcuate, with a well-marked spiral fold ; inner lip reflexed over the 

 umbilical region, and connected with the lip above by a thin white callosity. 

 Length -3 ; diameter *18 ; aperture, long -24, broad -17 inch. 

 Hab. Biver Avon, Christchurch. 



Animal olive brown sparingly speckled with yellowish white. Edge of 

 the mantle simple, slightly reflected over the shell. Foot broad and 

 rounded behind ; tentacles short, flat, triangular, with the eyes at the 

 inner bases. 



Dentition (pi. xii., fig. 10), 23-1-23, of which about 9 are laterals. Central 

 tooth slightly broader behind, the length rather more than twice the 

 greatest breadth ; the reflexed portion short, with a minute cutting point. 

 Laterals with the reflexed portion nearly as long as the base, triangular, 

 slightly sinuated on the inner and notched on the outer side. Cutting 

 points two, the inner one large, the outer small. The large cutting point 

 is simple in the inner laterals, but carries a small denticle in the outer 

 ones. Marginal teeth from three to many dentate, getting longer and 

 narrower outwards. Length of the radula rather more than twice its 

 breadth. Transverse rows of teeth nearly straight. 



Ova attached to stones or water plants in gelatinous lumps of 10-20 

 together. 



This species much resembles L. glutinosa of Europe, but in that species 

 the mantle is represented as covering nearly the whole of the shell. I have 

 not been able to compare the dentition, 



