MARYLAND GEOLOGICAL SURVEY 589 



deep ; the area between the auricle and the disk not sculptured ; characters 

 of interior not known. 



Pecten argillensis is identical with Pecten bellisculptus Conrad, which 

 was doubtless described from a type on which the delicate beaded sculpture 

 was better preserved than on the type of P. argillensis Conrad. The 

 species is one of the most abundant representatives of its genus in Mary- 

 land, but unfortunately it is so fragile that perfectly preserved individuals 

 are obtainable only with the greatest difficulty. 



Occurrence. MONMOUTH FORMATION. Brightseat, Brooks estate near 

 Seat Pleasant, 1 mile west of Friendly, Prince George's County. 



Collections. Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences, New Jersey Geological Survey, U. S. National Museum. 



Outside Distribution. Matawan Formation. Merchantville clay marl, 

 Woodbury clay, Marshalltown clay marl, and Wenonah sand, New Jersey. 

 Monmouth Formation. Navesink marl, New Jersey. ? Black Creek 

 Formation. North and South Carolina. Eutaw Formation (Tombigbee 

 sand member). Exogyra ponderosa zone, Mortoniceras subzone, Lowndes 

 County, and ? Prentiss County, Mississippi. Ripley Formation. Exo- 

 gyra costata zone, Georgia; Eufaula, Alabama; Chickasaw, Union and 

 Tippah counties, Mississippi. Extreme top of zone, Pataula Creek, 

 Georgia; Chattahoochee River, Alabama; Lowndes and Union counties, 

 Mississippi. 



PECTEN WHITFIELDI Weller 



Pecten tenuitestus Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 47, 

 pi. vii, figs. 5, 6. (Not Pecten tenuitestus Gabb, 1862.) 



Pecten wMtfieldi Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv. p. 

 468, pi. 1, fig. 14. 



Description. " Shell of small to medium size, broadly ovate exclusive 

 of the auriculations, the breadth of the shell being to the height as six is 

 to seven. Cardinal slopes straight, more than one-third the length of the 

 shell, and the anterior longest. Left valve very depressed convex, most 

 ventricose above the middle ; beak small and pointed. Auriculations large, 

 the anterior double the size of the posterior, very slightly rounded on the 



