Older Tertiary of Victoria. 25 



specimens of the European shell it may be noted that the latter 

 is a thicker, more robust and tumid shell, with a narrower hinge, 

 coarser umbo, and trigonal shape, the hinge characters are also 

 distinct, and the external sculpture gives further evidence for 

 separation. 



The present species is somewhat analagous to our very common 

 radially ribbed species, but is not as a rule so oblique in form, 

 and has its concentric ridging as a marked feature of contrast, 

 apart from other details. The late Sir F. McCoy identified the 

 common species of this genus from the lower beds of the Spring 

 Creek section near Geelong, as, without doubt identical, on a 

 comparison of actual specimens from English and German 

 localities, with Limopsis aurita, Brocchi, and there is no doubt a 

 very close resemblance in that instance, but I am not yet 

 prepared to make any more definite statement even in this case. 

 The mistake apparently made by Sir F. McCoy, if my interpreta- 

 tion be correct, was in the inclusion of the Mornington fossil as 

 identical with the common Spring Creek form. 



Modiola praepupta, sp. nov. (Plate II., Figs. 3, 4). 



Description. — Shell elongate-oval, markedly tumid, with 

 terminal umbo, and a remarkably steep slope to the ventral 

 margin. 



Anterior end narrow, about half the greatest width of the 

 shell, about the middle line strongly convex and rapidly 

 ascending from the anterior margin for a little more than one- 

 third the length of the shell, thence gradually sloping to the 

 posterior margin, spreading out and becoming flattish post- 

 dorsally. 



Ventral margin very straight, anterior margin somewhat 

 rounded, dorsal margin straight for a little less than half the 

 length of the shell, thence slightly convexly rounded to the 

 posterior, then more suddenly convex to the venti'al margin. 

 Greatest convexity ranging from the umbo obliquely across the 

 shell to about the junction of the posterior and ventral margins, 

 dorsally from this somewhat deeply excavated anteriorly but 

 rapidly shallowing out posteriorly. Surface with fine and very 

 close lines of growth, also with more or less defined undulations 



