MARYLAND GEOLOGICAL SURVEY 679 



Dimensions. Altitude 3.7 mm., latitude 4 mm., semi-diameter 1.4 mm. 



Type Locality. Brooks estate near Seat Pleasant, Prince George's 

 County. 



This small Yenerid is quite unique in the molluscan faunas of the 

 East Coast Upper Cretaceous. 



Occurrence. MONMOUTH FORMATION. Brightseat, Brooks estate near 

 Seat Pleasant, Friendly, McNeys Corners, Prince George's County. 



Collection. Maryland Geological Survey. 



Genus MERETRIX Lamarck 

 [Prodrome Nouv. Class. Coq., 1799, p. 85] 



Type. Venus Meretrix Linne. 



" Shell trigonal, plump, subequilateral, thin, smooth, with a vernicose 

 periostracum and a peculiar olivaceous tone of coloration; lunule and 

 escutcheon not distinctly defined ; cardinals three in each valve, with well- 

 marked anterior laterals; the middle left and two anterior right cardinals 

 entire, smooth, the others grooved or bifid; right nymph and posterior 

 left cardinal corrugated ; dorsal margins, beyond the hinge plate, grooved 

 to receive the edge of the opposite valve; internal margins smooth, the 

 pallial line with a shallow arcuate flexuosity but no angular sinus." 

 Ball, 1903. 1 



The genus was initiated in the Cretaceous. The recent species are most 

 abundant in the Pacific. 



MERETRIX CRETACEA (Conrad) Weller 



Mora cretacea Conrad, 1870, Am. Jour. Conch., vol. vi, p. 72, pi. iii, fig. 8. 

 Mora cretacea Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 167, pi. 



xxiii, figs. 16, 17. 



Mora cretacea Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 16. 

 Meretrix cretacea Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, 



p. 608, pi. Ixvili, figs. 4-7. 



Etymology: The specific name of the type. 



1 Trans. Wagner Free Inst. Sci., Phila., vol. iii, pt. vi, p. 1259. 



