379 



Mesodesma, sp. 



L. 10473. Cast of left valves no doubt referable to this genus, 

 not recognizable specifically ; from the Upper Miocene of Red Clitf, 

 llakuia river, Cautei'buzy, New Zealand. Sir James Hector Coll. 



Pamily MACTRIDJE. 

 Genus M A C T R A , Linnaeus. 

 [Syst. Nat. ed. 12, 1767, p. 1125.] 

 Crassatella, Lamarck, Mem. See. Hist. J^at. Paris, 1799, p. 85. 



Shell ovate-trigonal ; surface smooth or concentrically striated ; 

 hinge having a deeply bifid cardinal tooth placed in front of the 

 internal cartilage pit ; the latter is triangular, large, and slightly 

 oblique ; lateral teeth strong, compressed, both anterior and 

 posterior, double on the right valve and single on the left ; pallial 

 sinus round or angulate. 



In reference to the synonym Crassatella, see p. 363. 



Type. — Maclra slultorum, Linnaeus. 



Mactra axiniformis, Tate. 



18S7. Mactra axiniformis, Tate, Trans. Roy. Soc. South Aust. vol. ix. p. 170, 



pi. xvii. figs. \a-b. 

 1893. Mactra axiniformis, Tate and Dennant, id. vol. xvii. pt. 1, p. 225. 



Shell broadly ovately trigonal ; somewhat acuminately produced 

 posteriorly ; surface almost smooth in the umbonal region, remainder 

 of valve having concentric slender growth-ridges and striae ; ridges 

 fewer, more pronounced and rugose on the characteri.stic anterior 

 angulation, obliquely striated on the posterior carination. 



Dimensions. — Height 28 mm. ; length 39-5 mm. 



Form, and Loc. — Miocene : Muddy Creek, Victoria. 



L. 4840. Right valve of the adult. 



Presented by John Dennant, E-^q. 



L. 6612, L. 9881. Examples of both valves on wliicli concentric 

 colour bands are distinct. Purchased. 



