Maryland Geological Survey 519 



Yoldia longifrons Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 8. 

 Yoldia longifrons Weller, 1907, Geol. Survey of New Jersey, Pal., vol. Iv, 

 p. 381, pi. xxx, fig. 5. 



Description. — " Oblong, slightly ventricose, very inequilateral ; hinge 

 and basal margins parallel; anterior end acutely rounded, posterior 

 obtusely rounded ; cardinal teeth minute and very numerous." — Conrad, 

 1860. 



Type Locality. — Eufaula, Alabama. 



" Shell of moderate size, transversely subelliptical or subovate in form, 

 a little narrower behind than in front of the beaks. Beaks very small and 

 inconspicuous, situated rather more than one-third of the entire length 

 from the anterior end of the valve. Cardinal margin very gently declining 

 on each side of the beaks ; anterior end rounded, longest above the middle 

 of the height; posterior end more narrowly rounded, longest just below 

 the extremity of the hinge ; basal line very gently curved in the middle and 

 more abruptly so toward the extremities. Surface of the shell polished, 

 but marked by extremely fine concentric stria; of growth. In the interior 

 the hinge-line is marked by proportionally long curved teeth ; those on the 

 anterior side being largest and numbering fifteen or twenty, those of the 

 posterior side very small and numerous." — Whitfield, 1885. 



A single imperfect valve found in a nodule near Summit Bridge on the 

 Chesapeake and Delaware Canal has been referred to this species. 



Occurrence. — Matawax Formation. Post 105, Chesapeake and Dela- 

 ware Canal, Delaware. 



Collections. — Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences, U. S. National Museum. 



Outside Distribution. — Matawan Formation. Woodbury clay, New 

 Jersey. Eutaw Formation (Tombigbee sand). Exogyra ponderosa zone, 

 Mortoniceras subzone, of Georgia and Alabama. Ripley Formation. 

 Exogyra ponderosa zone, Union Springs, Alabama. Exogyra costata 

 zone, Eufaula, Alabama, and northern Mississippi. Selma Chalk. Exo- 

 gyra costata zone of east-central Mississippi. 



