658 SYSTEMATIC PALEONTOLOGY 



compressed than Whitfield'a type but this may be due merely to the con- 

 ditions of preservation. 



Occurrence. RAXCOCAS FORMATION. South feeder Noxontown Pond, 

 Delaware. 



Collections. Maryland Geological Survey, Columbia University. 



Outside Distribution. Eancocas Formation. ? Yincentown sand, 

 Manasquan marl, Xew Jersey. 



Superfamily LUCINACEA 

 Family LUC1N1DAE 



Genus MYRTAEA Turton 

 [Conchy. Insul. Britt,, 1822, p. 133] 



Type. Venus spinifera Montagu. 



" Shell elongate-oval or subrectangular, moderately convex or com- 

 pressed, dorsal areas obsolete, the sculpture of the disk chiefly concentric 

 and lamellar; the sculpture less pronounced in the middle of the disk and 

 frequently exhibiting a serrate appearance when the lamellae cross the 

 bounding carina of lunule or escutcheon ; internally with the left laterals 

 usually obsolete and only one right cardinal tooth ; cardinals entire ; liga- 

 ment and resilium deep-set but not internal; anterior adductor scar 

 lucinoid but rather short ; inner margins entire. 



" This group is paralleled in Pliacoicles by several others which want the 

 anterior right cardinal in the adult, but in Myrtcea the single right car- 

 dinal seems to be normal, while in the subdivisions of Phacoides its 

 absence is due to degeneration during the growth of the individual or to 

 the dynamic results of the inthrusting of the lunule, which occupies the 

 space where the anterior cardinal would otherwise develop." Dall, 1903. 1 



The genus is reported from strata as old as the Jurassic. There has 

 been a tendency to indiscriminately assign all lucinoids to Lucina, and it 

 is probable that the occurrence of Myrtcea in the Mesozoic strata has been 

 underestimated. 



'Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. v, p. 1357. 



