40 



DESCRIPTIONS OF TWO NEW SPECIES OF TAS- 

 MANIAN ERESH-WATER SHELLS. 



• Bt W. E. Pbtteed. 



Plate XLIV. 



ANCYIiUS IE,VIN(E. N. SP, 



Shell thin, diaphanous, horney-brown, delicate ; inflated, 

 with about 12-14 distant, distinct, irregular, somewhat 

 angular radiating riblets, concentrically, finely, irregularly 

 striate with a silky appearance ; apex prominent, recurved 

 dextrally ; aperture orate, margins expanded ; interior 

 shining, plainly showing the impression formed by the 

 riblets. 



Length, 19 mill. 



Breadth, 14 „ 



Alt., 7 ,, 



Habitat — the Great Lake (Irvine). 



This wonderfully fine and interesting addition to our 

 Mollucan fauna was obtained by Mr. R. Irvine, of Launceston, 

 during an excursion to the Lake district. It was found 

 attached to the rocks in the shallow margin of the lake, and 

 although apparently numerous at the particular locality 

 visited but only a very limited number of examples were 

 collected. Associated with it was found Cyclas Tasmanica, 

 Tenison Woods, and an apparently new sj)ecies of Physa. 

 Unfortunately I have not had an opportunity of examining 

 the animal or lingual membrane. This species is not only 

 the finest form of the genus discovered in this island, but is 

 also by far the finest in the world. It is quite distinct from 

 all the species hitherto known — the nearest is our Ancylus 

 Cumingianus Bourguignat (Pro. Zoo. Soc, 1853) from above 

 New Norfolk, but from it may be known by its much larger 

 size and by the unique character of being radiately ribbed. 

 The few species described from Australia are all very minute 

 and have no resemblance to either A. Cumingianus or the 

 form now described. It is dedicated to Mrs. Irvine, sen., a 

 great lover of shells. 



