BY C. HEDLEY. 203 



Tate & May have mergerP A. radula in Anomalocardia 

 carpenteri, Dunker. The crenulated inner margin figured in that 

 species forbids such a union. 



Area pistacliia occurred to me in Twofold Bay, N.S.W., and 

 Miss L. Parkes has taken it in Sydney Harbour 



Arca lischkei, Dunker. 

 (Plate ix., figs. 29-34.) 



Arca trapezia, Deshayes; Hanley, Cat. Recent Shells, Append. 

 1856, p. 374, pl.xviii., f. 40. 



Anomaloca7'dia lischkei, Dunker, ISTovitates Conchologicse, 

 Moll. Mar. Partxiii., March 1868, p. 115, pi. xxxviii., figs. 14, 15, 

 16. 



Anomalocardia trapezia, Deshayes; Jack & Etheridge, Geol. 

 Queensland, 1892, p. 641, pi. xxxvi., figs. 10, 11, 12. 



In studying Australian marine mollusca, I have found most 

 difficulty in naming, not the rarer forms, but the commonest 

 shells, such as Cliione lagopus, Pecten medius, and the present. 



Various names have been assigned by London writers to the 

 Sydney Mud-cockle, none of which are satisfactory. The 

 excellent figure and description of an ordinary form of this vari- 

 able species by Dunker, appears to have hitherto escaped recog- 

 nition as applying to the Australian shell. Its first appearance 

 in literature is an observation by J. Macgillivray, f who described 

 it as stacked in heaps, several hundred yards in length and more 

 than twenty feet in depth, in aboriginal kitchen-middens at 

 Broken Bay and Brisbane Water, N.S.W. In a footnote Forbes 

 and Hanley identified the species as Arca trapezia, Deshayes. 1 



But that species, of which A. lohata, Reeve, is acknowledged § 

 by its author to be a synonym, is a native of Semblas, Mexico, 



* These Proceedings, xxvi. p. 486. 

 t Ann. Mag. Nat. Hist (2) ii. p. 30, July, 1848. 

 + Revue Zoologique, Soc. Cuv. ii. Dec, 1839, p. Soa; and Mag. de Zool. 

 2nd ser. ii. 1840, Moll. PI. xxi. 



S Conch, Icon, errata to Arca. 



