94 Proceedings of tJce Royal Society of Victoria. 



Dimensions. — Autero-posterior diameter, 40 mm.; umbo-ventral 

 diameter, 18 mm.; greatest height at the middle diametei', 

 19 mm.; thickness through both valves, 18 mm. 



Locality. — Dredged alive from about 6 fathoms off Rhyll, 

 Phillip Island, Western Port. 



Observatiojis. — Tliis form may be readily distinguished from 

 our other species of this genus by its regular tumidity, and its 

 remarkable uniform height. 



Type in Mr. Gatlift''s collection. 



Observations on our commonest species of Chione. 



Representatives of the genus Chione are particularly common 

 on many parts of the shores of Port Phillip, but there are three 

 well-marked forms which require special treatment owing to the 

 confusion existing as to their correct naming. 



These species are the following : — 



Chione strigosa, Lamarck. 

 Chione scalarina, Lamarck. 

 Chione peronii, Lamarck. 



The most abundant forui . is commonly referred to as C. 

 strigosa, Lamarck, and this may be identihed by its enlongate- 

 ovate form, anastomosing concentric ridges, which are distinctly 

 crossed by continuous radiating striae. 



The next most frequently met with is usually known as 

 C. scalarina, Lamarck, and this diii'ers from 0. strigosa by its 

 more attenuate posterior, by its regular concentric ridges develop- 

 ing into lamellae anteriorly and posteriorly, and the absence of 

 the radiating striae. 



The third form to which we consider Lamarck's name C. 

 peronii properly belongs, may be identitied by its more inflated 

 form and flattened concentric ridges. 



All these forms vary in colour botli externally and internally, 

 each form being sometimes colourless externally, in fact so great 

 is the variation on difierent points, that but for tlie above 

 apparently constant characters tliey might nearly be regarded as 

 extreme variations of one species. 



We give in the succeeding part of our Catalogue of the Marine 

 yiiells of Victoria, Part VII. , a limited number of references to 

 these species, which we consider in each case refers to the same 



