305 



valve has two prominent muscle-markings in the "circumscribed 

 area" ; whilst tlie calcified, plugged perforation is narrow, elongate, 

 and slightly oblique. The external ornament of both valves is 

 more scaly and imbricated, and the irregular radiating plications 

 are more prominent and much more numerous than in P. zealandica. 

 Gray ; whilst it differs also from P. tone, not only in the main 

 features of the external ornament, but in having a relatively smaller 

 byssal notch and in the shell not being rounded. 



Dimensions. — Height 49 mm. ; length 47 mm. 



Form, and Loc. — Miocene (?) : Parimoa, New Zealand. 



L. 10520. Complete specimen of the adult, byssal notch calcified. 

 Transferred from the Museum of Practical Geology. 



L. 10521, L. 10528. Several examples of both valves. 



W. B. D. Mantell Coll. 



Placunanomia, sp. 



L. 10516. Cast of the interior of the non-perforated valve 

 of a species, showing well-marked radiating ridges ; too imperfect 

 for identification. Miocene : Akuakua, east coast of Auckland, 

 New Zealand. Sir James Hector Coll. 



Family DIMYID^. 



Genus DIMYA, Rouault. 



[Mem. Soc. Geol. France, 2^ ser. t. iii. pt. 2, 1850, p. 470.] 



Shell inequivalve, suborbicular, equilateral, flat, adhering by one 

 of the valves ; ligament internal, median, lodged in an elongated 

 groove ; no cardinal teeth ; interior of the valves typically showing 

 a linear row of denticles parallel to the margin of the shell. 



After discussing the systematic position of the genus. Professor 

 Tate remarks that the two new Australian species which he assigns 

 to Limy a "have the general aspect of Plicatula rather than of 

 Ostrea ; whilst the two diverging cardinal ridges make an approach 

 to Placuna, though functionally different." That author is mistaken, 

 however, in supposing that Bimya was founded on a shell from the 

 Parisian Eocene ; it came from Bos d'Arros, in the south of France. 



Type. — Bimya deshayesiana, Ilouault. 



z 



