236 SMITH : NOTES ON AUSTRALIAN SPECIES OF SHELLS. 



The generic division Gabbia, proposed by Tryon for this 

 species, appears to be altogether unnecessary. The character 

 upon which he founded the group was a supposed peculiarity 

 in the operculum which he describes! as " paucispiral, 

 calcareous." His own figure and the shells before me show 

 that the operculum is not paucispiral, but normally concentric, 

 as in other species of Bithinia. Such being the case, the genus 

 Gabbia may be cast aside, but as the specific name imposed 

 upon this species must, according to the laws of priority be 

 retained, it becomes necessary lo re-name the form from 

 Victoria River, which I described as B. australis ; this I would 

 therefore propose should be called B. tryoni. 



Messrs. Tate and Brazier, in their Check List of the Fresh- 

 water Shells of Australia,! have already recognised the inutility 

 of the section Gabbia. 



Segmentina australiensis. 



A large series of specimens from Waterloo, Sydney, which 

 I consider belong to this species, differ from the type in some 

 respects. None of them are of so dark a colour, and not a 

 single specimen has the internal lamellae nearly so strongly 

 developed. Some have only two very small tubercles, one 

 upon the upper and one upon the lower wall of the body-whorl ; 

 others are entirely destitute of teeth of any description, and but 

 very few exhibit the parietal lamella so conspicuous in the type. 

 The greater or less development of these internal processes is 

 probably regulated by age, so that in old shells they would 

 more frequently be present, and more strongly developed than 

 in younger specimens. 



In a second series from Eundaberg, Queensland — also 

 presented to the Museum by Mr. Brazier — I cannot detect a 

 single example with any indication of teeth, but in all other 

 respects these shells agree exactly with those from Waterloo. 



t American Journ. Conch., 1865, vol. i., p. 220, pi. 22, f. 7. 

 X Proc. Linn. Soc, New South Wales, 1882, vol. vi., p. 562. 



J.C , v., Oct., 1887. 



