230 Proceedings of the Royal Society of Victoria. 



the beak backwards and downwards, practically straight, then 

 roundly truncate to meet the very slightly convex ventral 

 margin. The usual sized shell is ornamented with from 40 to 50 

 raised rounded narrow concentric ridges, which become lamellai' 

 anteriorly and posteriorly, interspaces very much narrower than 

 the concentric ridges, becoming wider ventrally. The concentrit- 

 ridges are so close as to prevent any radial ornamentation being 

 seen at first, but, on holding the specimens with a strong light 

 beliind them, an exceedingly tine and close radial ribbing is just 

 visible. Interiorly the shell margin is very minutely crenulated. 



Diinoisions. — Average specimens give the following measure- 

 ments, antero- posterior diameter, 11 "5 mm.; umbo- ventral 

 diameter, 9 mm.; thickness through both valves, 6 mm. The 

 largest specimen at present in my possession measures along its 

 antero-posterior diameter, 16 mm., and umbo-ventral diameter, 

 13 mm. 



Locality. — Common in the Lower Eocene sands and clays of 

 (Spring Creek, 14 miles south of Geelong. 



Observations. — This species is very closely allied to Chione 

 propinqua.^ T. Woods, but is a much smaller shell than the adult 

 of that species ; compared with young examples of C. propiiujiia 

 of about the same size from the Miocene beds of Muddy Creek, 

 the new species differs in form, is a thinner shell, is much more 

 convex, the umbones are more prominent, the concentric ridges 

 are liner and more numerous, the radial ribbing is obscure and is 

 not continued on to the concentric ridges or lamelke. These 

 differences seem adequate to my mind to justify the proposal of a 

 new specitic name for this shell, particularly as they appeared 

 very constant throughout my examination of upwards of sixty 

 examples. 



T have much pleasure in attaching to this shell the name of 

 my friend, Mr. T. S. Hall, M.A., Demonstrator and Assistant- 

 Lecturer in Biology at the Melbourne University. 



In conclusion, I must expi'ess my indebtedness to Professor 

 W. Baldwin Spencer, and tender to him my liest thanks for 

 photographing these shells for lithographic purposes. 



