265 



shortly acuminated; a slightly-curved keel defines the dorsal area, 

 which is striated and moderately impressed ; the lunule is very 

 narrow and defined. 



The concentric linie are regular, about 30, stout, elevated, and 

 compressedly-rounded, separated by a little wider, flat furrows; 

 they are slightly incurved as they approach the anterior margin, 

 and more conspicuously so towards the posterior keel, though 

 there is no appearance of a second keel. 



Dimensions. — Antero-posterior, 8 ; umbo- ventral, 5 ; sectional 

 diameters, 3*5 mm. 



Numerous examples dredged in life by Dr. Yerco (after whom 

 the species is named) in Yankalilla Bay ; also in shell-sand, 

 Holdfast Bay (E. T.). 



This is not the young of L. C7rcssa, which at the same size has 

 a well-pronounced second keel defining the rostral area. It makes 

 an approach to L. Dohrni, Hanley, but has not so straight a 

 hinge-line, and is more convex. 



A Second Supplement to a List of the 

 Lamellibranch and Palliobrangh Mol- 

 LuscA OF South Australia. 



By Professor Ralph Tate, F.L.S., F.G.S. 



[Read September 8, 1891.] 



Chiefly through the dredging operations conducted by Dr. 

 Verco during the past summer several additions have been made 

 to the Lamellibranch-fauna of South Australian waters ; several 

 of these are of extreme interest, and I am constrained to found 

 no less than six new species, which are described in the preceding 

 pages. 



Addenda and corrigenda to previously recorded species are 

 placed within brackets. 



Thracia SpeciOSa, Aufja>^, Proc. Zool. Soc, 1869, t. 2, fig. 12, p. 48. 



Compared with T. modesfa, this species is oblong and more in- 

 equilateral. 



A left valve, dredged at 12 fathoms in Yankalilla Bay by Dr. 

 Yerco, agrees fairly well with Angas' figure of his T. speciosaj 

 though its anterior side is longer, and the height is slightly less. 

 Length, 19-5 mm.; height, 10*5. 



