326 RECORDS OF THE AUSTRALIAN MUSEUM. 



valve. At first sight the general appearance reminds one of the 

 Corhnla group, l)ut any alliance therewith is at once discounted 

 by the edentulous nature of the articulus. 



I have examined a large number of internal casts, but only 

 with negative results ; all the internal features of the test must 

 have been very weak. 



In view of future research, I would like to point out that 

 Moore described a small bivalve as Mactra triyotialis", and said a 

 thin slab from the Nive River Downs "appears to be almost 

 composed of this little shell." Moore's figure was drawn 

 from a very poor specimen, that is certain. It is equally 

 clear the figure in question, as it stands, does not represent the 

 present species. At tlie same time allowing for Moore's very 

 brief descriptions of his Australian shells, and the often imperfect 

 material figured, there is the possibility, both being gregarious, 

 that M. trigonaJis and C. chufvs are one and the same ; on the 

 other hand the test of the latter is not thin, and supposing them 

 to ultimately prove identical, they are not a Mactra. 



Gemis Cytherea, Lamark, 1806. 



(Ann. Mus. Hist. Nat. Paris, 1806, vii., p. 1.32). 



Cytherea (?) mookei, Eth.fil. 



(Plate Ixii., figs. 1-3). 



Cyjyrina (?), sp., Hudleston, Geol. Mag., i., 1884, p. 341, pi. xi.^ 

 f. 7 a and b. 



Cytherea (Cyprina?) Moorei, Eth. fil., Geol. Pal. Q'land, etc., 

 1892, p. 474, pi. xxxiv., f. 12 and 13. 



Sp. Char. — Shell ovate, width and length nearly equal, in- 

 equality of the sides well marked. Valves tumid in the umbonal 

 regions frequently through the presence of well marked epiostraca ; 

 compres.sed ventrally. Cardinal margins sharply angular ; lunule 

 widely diamond or lozenge-shaped ; escutcheon undefined. 

 Anterior and posterior ends very unequal, the latter much the 

 larger, occupying at least two-thirds of the shell width, and 

 slightly obtusely produced ; anterior and ventral margins are 

 well and regularly rounded, but the posterior is more sharply 

 I'ounded than the anterior. Sculpture concentric, of very regular 

 grooves with flat interspaces. 



J 1' Moore — Quart. Joiirn. Geol. Soc., xxvi., 1870, p. 262, pi. xiv., f. 6.] 



