21 



inconstant characters, I may refer to Mr. Woods' statement 

 with respect to Physa ciliata — " This ciliated form is quite 

 exceptional in the genus, only 07ie other being found in India^ 

 So far from being exceptional in Northern Tasmania, I have 

 found the reverse to be true. Nearly all the species of Physa 

 are ciliated, especially in yoimg individuals, in the following 

 localities, viz. : North and South Esk E-ivers, Avoca, Distil- 

 lery Creek, Racecourse Creek, Launceston ; Lament's Creek, 

 Punch Bowl, Kerry Lodge Creek, Pools, St. Leonards ; and 

 First Basin, Deloraine ; Circular Head, George Town. I 

 have since learned, from Mr. Woods himself, that a ciliated 

 shell, closely allied to a Northern species, aboiuids in the 

 neighbourhood of Melbourne, thus adding another link to 

 the fresh water fauna of the two near though isolated regions. 

 It may be allowed, therefore, that the presence or absence of 

 cilise is a very unreliable character. The ciliae, as a rule, are 

 so remarkably delicate that the mixing u}) of several speci- 

 mens in the same box is apt to rub off every trace of those 

 beautiful ciliated lines so conspicuous on the surface of the 

 shell when carefully removed from the water. 



I have noticed that in the young shell of P. Biemen- 

 ensis (Sow.), the ciliae are usually in two or three con- 

 tiguous rows on the crown of the whorl immediately below 

 the suture. In another species which I have not yet satis- 

 factorily determined, I have counted as many as 25 rows 

 disposed also in transverse curves on the last whorl. Some- 

 times, when washed off, the former growth of cilise has left 

 a permanent wavy decussate structure on the transparent 

 pale horny shell. This feature is another point which Mr. 

 Woods states is peculiar in an Indian species. When we 

 consider the delicacy of the cilise it is easy to understand 

 that dead specimens, frequently handled or rubbed against 

 each other, would reveal no trace to the classifier. Hence I 

 maintain that the character is unreliable for classification 

 purposes. 



I have found a specimen of Pisidium Tasmanicum, with a 

 white silvery-ciliated umbo, near Avoca. Prom Christchurch, 

 New Zealand, I obtained a single specimen of a BithyneUa, 

 collected by Mr. T. E. Atkinson, and, although the lip is 

 imjDcrfect, I am satisfied that it is closely allied to B. Tasma- 

 nica (Tenison- Woods).* This, again, may prove another 

 link in the distribution of fresh water shells. 



In regard to limited distribution of peculiar forms, it must 

 be borne in mind that fresh water shells hybernate during a 



* Mr. Woods, subsequently to the readmg of this paper before 

 the Royal Society of Tasmania, had come to a similar conclusion, 

 in referring, with others, the N.Z. species to B. corcdla (Gould). 



