18 



end, situated in a line with the upper tentacle oq the right 

 side. 



Mandible crescent-shaped, not rostrated, vertically grooved 

 and interstriated, denticulated on the margin. 



Lingual ribbon of 96 rows of an infinite number of similar 

 lanceolate teeth. 



Dimensions: — Total length when crawling (without ten- 

 tacles), 30 millimetres; total width when crawling, 9 milli- 

 metres. (Measures made by Mr. Petterd.) 



Locality : — Near Launceston (W. F. Petterd) ; Southport 

 (B. R. Dyer). 



A CONTRIBUTION TO OUR KNOWLEDGE OF THE 

 UNIONID^ OF THE LAUNCESTON TERTIARY 

 BASIN. 



By R. Etheridge, Jun., F.G.S. 



(Of the British Museum), 



Corr. Member R. Socs. Tasmania, Victoria, and of the 

 Linnean Society of New South Wales. 



[Bead 13i/i A]jril, 1880.] 



Several interesting papers having recently apj^eared on the 

 Tertiary beds of the Launceston Basin, by Mr. R. M. John- 

 ston, it struck me that the description of two forms of Unio, 

 occurring in these beds, might be accej^table to the Royal 

 Society, especially as the subject appears to be, comparatively 

 sj^eaMng, a new one. 



So far as I am aware, the literature relating to the occur- 

 rence of this genus in the Tertiary and Post Tertiary 

 formations of Australasia is very limited. 



Omitting, as not coming within the scope of this present 



