355 



Trigonia acuticostata, M'Coy. 



1866. Trigonia lamarckii, H. M. Jenkins, Geol. Mag. vol. iii. p. 201, pi. x. 



figs. 3-7 [non Math.). 

 1866. Trigonia acuticostata, M'Coy, Geol. Mag. vol. iii. p. 482, fig. 1. 

 1875. Trigonia acuticostata, M'Coy, Prod. Pal. Yict. dec. ii. p. 21, pi. xix. 



figs. 1, 2. 

 1878. Trigonia acuticostata, E. Etheridge, jun.. Cat. Aust. Foss. p. 157. 

 1886. Trigonia acuticostata, Tate, Trans. Roy. See. South Aust. vol. viii. 



p. 145. 



Distinguished by the absence of transverse ridges, the ornamcut 

 consisting of elevated radial costai, on which are numerous, equi- 

 distant, sharp denticles ; the costae are rather widely separated, 

 the interstices exhibiting closely-set lines of growth. 



Dimensions. — Height 24 mm. ; length 28 mm. 



Form, and Loc. — Miocene : Yictoria. 



L. 353. Two examples of a variation in which the shell is 

 rather less oblique than in typical specimens, whilst the denticles 

 on the costse are well elevated ; from Baimsdale. 



Presented hy JF. H. Grigson, Esq. 



L. 9850. Eight valve ; from Muddy Creek. Purchased. 



Trigonia, sp. 



L. 10558. Internal cast of right valve, species indeterminable. 

 Eocene (?) : Waipara, New Zealand. Sir James Hector Coll. 



Family UNIONID^. 

 Genus UNIO, Retzius. 



[Diss. Nova Test. Genera, 1788, p. 16.] 



Shell commonly equivalve ; nacreous in the interior ; umbones 

 placed anteriorly, frequently corroded ; surface smooth, plicated 

 or tuberculose ; ligament prominent, long ; hinge of right valve 

 carrying two anterior lateral teeth, and cue long posterior lateral 

 tooth ; hinge of left valve composed of one anterior lateral tooth, 

 one cardinal tooth placed under the umbo, and two long lateral 

 posterior teeth ; pallial line entire ; surface ornament usually 

 simple. 



'Type. — Mya margaritifera, Liunseus. 



