48o CRETACEOUS PALEONTOLOGY. 



member of the Navesink and Red Bank faunas. Whitfield men- 

 tions Burlington as one of the localities for the species, which 

 would indicate a lower horizon, but it has not been met with in 

 the recent collections of the Survey anywhere below the Nave- 

 sink except one occurrence in the Marshalltown. It is quite prob- 

 able that the locality recorded with Whitfield's Burlington speci- 

 men was intended for Burlington County, as many specimens in 

 the Philadelphia Academy collections are so' labeled, and in that 

 case the specimen doubtless came from the Navesink. 



Formation and locality. — Marshalltown clay-marl, near 

 Swedesboro (179) ; Navesink marl, near Walnford (149), near 

 Crawfords Corners (126'^), near Holmdel (128^, 127), Marl- 

 boro (131), near Freehold (133), Crosswicks Creek (149, 195), 

 Mullica Hill (169); Red Bank Sand, Red Bank (116, 123), 

 Shrewsbury River (119); Tinton beds, Tinton Falls (no), 

 Beers Hill cut (129^), near Freehold (132). 



Geographic distribution. — New Jersey. 



Pecten simplicius Conrad. 

 Plate LI., Pig. 6. 



i860. Pecten simplicius Con., Jour. Acad. Nat. Sci. Phil., 2nd 



ser., vol. 4, p. 283, pi. 46, fig. 44. 

 1 861. Pecten simplicius Gabb, Synop. Moll. Cret. Form., p. 



216 (160). 

 1864. Sincyclonema ? simplicus Meek, Check List Inv. Foss. 



N. A., Cret. and Jur., p. 7. 

 1868. Pecten simplicus Con., Cook's Geo!. N. J., p. 725. 

 1876. Sincyclonema simplicius Gabb, Proc. Acad. Nat. Sci. 



Phil. (1876), p. 319. 

 1886. Amusium simplicum Whitf., Pal. N. J., vol. i (Monog. 



U. S. G. S., vol. 9), p. 51, pi. 7, figs. 11-12. 



Description. — "Shell small, barely half an inch in extreme 

 height, and of equal width; discoid or very depressed convex, 

 nearly or quite equilateral ; margins of the shell somewhat regu- 

 larly rounded; hinge-line a little less than half the width of the 

 shell, and slightly rising from the center toward the extremi- 

 ties. Auriculations moderately large, the anterior side largest, 



