597 



with a groove between it and the border for the reception 

 of the corresponding anterior tooth of the left valve, which 

 consequently lies outside the right tooth and is somewhat 

 longer than this, so as to extend slightly beyond it anteriorly. 

 Just outside the base of the right tooth is a short lanceolate 

 elevation, scarcely to be dignified with the name of a tooth, 

 fitting into a complementary depression in the left valve. 

 In the right valve, in front of the horn, outside the gutter 

 for the left anterior tooth, is a linear roughened depression 

 within the border of the valve, for the attachment of a long 

 narrow ligament, which passes beneath the base of the horn, 

 within the margin of the shell, and here gradually widens. 

 Here, too, the area is very slightly hollowed out, and the 

 margin of the hingeplate or ligament-plate is also somewhat 

 excavated, as though the ligament here were thicker and 

 even projected into the cavity of the shell. Beyond the horn, 

 posteriorly, the ligamental depression gradually narrows 

 again until it vanishes, being rather more than twice as long 

 as the anterior part. There is a corresponding rough liga- 

 mental area in the left valve, though the hollowing of it 

 beneath the horn does not seem to be so decided. In the 

 posterior third is a linear depression to receive the sharp 

 margin of the right valve. 



Judging from the several detached valves, taken at the 

 same spot as the perfect specimen, the following changes 

 would seem to occur with advancing age. The two anterior 

 teeth become much larger and more solid, and especially 

 does that in the left valve, where it bends in ventrally at 

 the end so as apparently to curve round the anterior end 

 of the right tooth. The hingeplate becomes very solid and 

 straight (losing the sub-umbonal depression), except near the 

 left tooth, where it also curves. The ligamental area gets 

 wide and rough and deep, and in some cases winds round 

 the dorsal surface of the left tooth, so as to make a depression 

 in the margin of the valve. 



The presence of the very valid anterior teeth makes the 

 name of the new genus created for this species, Edenttellina, 

 inappropriate, as it is by no means edentulous. 



"Additions to the Flora of South Australia, No. 

 10," by J. M. Black; "South Australian Eucalypts and 

 their Essential Oils," by R. T. Baker, F.L.S., and H. G. 



