686 SYSTEMATIC PALEONTOLOGY 



straight, oblique ; margins rounded ; umbonal slope undefined and regu- 

 larly convex with post-umbonal slope. This is the first species found in 

 America, and represents an interesting exclusively Cretaceous genus. The 

 hinge fortunately can be obtained in perfection at Snow Hill. The genus 

 is common to the Senoniah strata in America, Europe and Southern 

 India." Conrad, 1875. 



Type Locality. Snow Hill, North Carolina. 



Ligament external, opisthodetic, nymphs elongated and produced more 

 than half the length of the dorsal margin ; cardinals three in number in 

 right valve, two in left; the anterior and middle cardinals of the right 

 valve rather short, simple and not very heavy, diverging at rather a small 

 angle from beneath the umbones, the posterior cardinal laminar obliquely 

 elongated and placed far back toward the nymph; cardinals of the left 

 valve two in number, the anterior laminar, the posterior shorter but rather 

 stouter, diverging beneath the umbones at an angle of about 25 ; space 

 between the anterior cardinal and the dorsal margin wider than that 

 between the posterior cardinal and the nymph ; muscle impressions rather 

 large, unequal, the anterior elongated, the posterior subcircular, situated 

 above the median horizontal near the extremities of the hinge plate ; pal- 

 lial sinus broad, moderately deep, horizontally directed, obtuse; inner 

 ventral margins simple. 



Occurrence. MATAWAX FOEMATION. Cassidy's Landing, Cecil 

 County. 



Collections. Maryland Geological Survey, U. S. National Museum. 



Outside Distribution. Black Creek Formation. North and South 

 Carolina. Ripley Formation. Exogyra ponderosa zone. Barbour County. 

 Alabama. 



Genus CYPRIMERIA Conrad. 

 [Proc. Acad. Nat. Sci., Phila., 1864, p. 212] 



Type. Cytherea excavata Morton. 



Lentiform; hinge of right valve broad, with a bifid oblique cardinal 



tooth under the apex, and two oblique acute anterior teeth, with an inter- 

 Etymology: KvTrpis, Cypris, a surname of Venus and a Lamarckian genus 



of bivalves. 



