S35 



Subgenus PLAGIARCA, Conrad. 



[Geol. Siirv. North Carolina, vol. i. 1875, App. A, p. 4.] 



Shell transversely elongate ; cardinal border straight, narrow, 

 angulate at the extremities ; teeth oblique ; surface ornamented 

 by radiating ribs and often punctate ; ligamental area narrow. 



Tjipe. — Barhatia carolinensis, Conrad. 



Area (Plagiarca) cainozoica, Tate (sp.). 



1886. Macrodon cainozoiciis, Tate, Trans. Roy. Soc. South Aust. vol. viii. 



p. 143, pi. X. fig. 4. 

 1889. Macrodon cainozoicus, Dennant, id. vol. si. p. 50. 

 1893. rifigiarca cainozoica, Tate and Dennant, id. vol. xvii. pt. 1, p. 224. 



The concentric ridges on the surface of the valves are more 

 prominent than the broken radial lineations ; umbones close to the 

 anterior border ; hinge area narrow, liueate ; posterior border 

 olilique, rounded and produced underneath ; centre of the cardinal 

 bordt'r edentulous. 



Dimensions. — Height 10 mm. ; length 22 mm. 



Form, and Loc. — Eocene : Muddy Creek, Yictoria. 



L. 4807. Two specimens of the neanic stage of growth. 



Presented ly John Demiant, Esq. 

 L. 6597. Examples of the adult. Purchased. 



L. 9875. Series illustrating stages of growth. Purchased. 



Subgenus FOSSULARCA, Cossmann. 

 [Ann. Soc. Eoy. Malac. Belg. t. xxii. 1887, p. 138.] 



Shell subquadrangular, inequivalve; surface trellisod ; ligamental 

 area narrow, having under the umbo a small triangular pit ; teeth 

 almost equal in size ; more or less oblique. 



Closely allied to Limopsis, but the cardinal pit is not so deep, 

 the disposition of the teeth is different, and the form of the valves 

 is that of Area. 



Type. — Area quadrilafera Lamarck. 



