56 
The cardinal fold of the left valve — the “ little win^ ” of Waagen — 
is much larger than that of the right, and unlike that of the latter does not 
project at riglit angles to the plane of the liinge-plate, hut upAvards and 
slightly outwards, or nearly parallel to the plane. The projection is large, 
heavy, and hlunt, on its inner side concave and dorsally ridged and furrowed 
like the lunular depression. It is this fold which, Alvhen the valves are in 
apposition and closed, is seen to project from beneath the left umbo like a 
little “ear” or “wing,” as IVaagen termed it. If the tAvo halves of the 
articulus of Eurydesina he noAV regarded from the point of vieAV of proportion, 
the absolute inecpiality of the valves becomes at once apparent, Avithout any 
reference to the external aspect, Avhich is at times misleading. 
The nearly horizontal cardinal fold of the right valve rests under the 
concave surface of the fold of the left Aalve, Avhilst the upAvardiy directed 
fold of the latter in its turn fits into a “ chondrophoral”-like de])ression of the 
right valve, Avhere it forms a very marked feature. It is situated heloAv the 
anterior end of the resilifer, is rather spoon-shaped in outline and section, 
and obliquely inclined ; the anterior end abuts against the ridge connecting 
the umhonal apex Avith the cardinal fold. 
These folds to some extent perform the function of the teeth of other 
Pelecypoda, hut they are no more teeth, strictly speaking, than is the 
thickened ridge beloAv the anterior end of the resilifer of the left valve in one 
of the Pearl Oysters — 2Ieleagrina maxima, Jameson — Avhich Avorks against 
a thickened and flattened surface in a corresponding position on the right 
valve of the same species. 
Morris described the j)resence of a “ large obtuse tooth in the right 
valve, left inconspicuous.”' Dana speaks of a “ large rounded prominence or 
tooth” in the left Andve, fitting into “a depression somewhat anteriorly.”^ 
To this prominence in the right valve, Stoliezka assigns the name of 
cardinal tooth : — “One large suhconical cardinal tooth in the right valve, 
someAvhat curved upAvards, and corresponding to a pit in the left.”® 
This tooth or prominence is shown on the articulus of the left A'alve 
of Prech’s first figure of Leiomyalina antarcHca '^ ; but in his later figure — 
* Morris in Strzelecki — Loc. cit., p. 275. 
* Dana — Op. cit., p. 690. 
’ Stoliezka — Loc. cit., p. 226. 
* Freeh — AbhandL, loc. cit., j). 203, fig. 22. 
