Maetlajtd Geological Suetey 527 



Outside Distribution. — Matawan Formation. Merchantville clay marl 

 and Marshalltown clay marl of Xew Jersey. Monmouth Formation. 

 Xavesink marl and Tinton beds of Xew Jersey. Ripley Formation. 

 Exogyra costaia zone, Georgia ; Eufaula, Alabama ; northern Mississippi. 

 Extreme top of zone, Pataula Creek, Georgia, and Chattahoochee River, 

 Alabama. 



Nemodon stantoxi n. sp. 

 Plate XIX, Fig. 15 



Description. — Shell transversely elongated, rudely trapezoidal in out- 

 line, the posterior basal margin obliquely produced; dorsal margin hori- 

 zontal, more than two-thirds the entire length of the shell ; anterior lateral 

 margin obliquely truncated dorsally and meeting the hinge at an angle of 

 50° or 55°, broadly and smoothly rounded ventrally: posterior lateral 

 margin also obliquely truncated, meeting the dorsal margin at an angle 

 of approximately 65°, produced ventrally and rounding rather sharply 

 into the base ; ventral margin more sharply upcurved behind than in front, 

 straight medially but not parallel with the dorsal margin ; umbones small, 

 acute, proximate, placed a little in front of the median line; umbonal ridge 

 acute in the umbonal region but becoming broader and more obtuse away 

 from the umbones and obsolete near the margin ; external surface sculp- 

 tured with a microscopically fine radial lineation, least feeble anteriorly 

 and over the umbonal ridge ; hinge imperfect in the umbonal region of the 

 unique type ; distal teeth laminar, elongated parallel to the hinge margin, 

 apparently two on each side, the dorsal tooth the more produced in the 

 anterior series, the ventral the more produced in the posterior ; characters 

 of interior not known. 



Dimensions. — Altitude, 16.5 mm.; latitude 33.5 mm.; semi-diameter 

 4.5 mm. 



This species is named for Dr. Timothy W. Stanton, Chief Paleontologist 

 of the U. S. Geological Survey. 



Occurrence. — Mokmouth Formation. Brightseat, Prince George's 

 County. 



Collection. — Maryland Geological Survey. 



