468 CRETACEOUS PALEONTOLOGY. 



line. The dimensions of an imperfect impression of a left valve 

 are: height, about 40 mm.; width, 41.5 mm.; length of hinge- 

 line, about 22 mm. Auriculations of moderate size, subequal, 

 but slightly depressed below the general surface. Surface marked 

 by about thirty, low, rounded ribs, which are much narrower 

 than the flattened interspaces, the stronger ribs continue to the 

 beak and never bifurcate, the smaller ones being added by inter- 

 calation, the auriculations are entirely free from radiating ribs ; 

 besides the radiating ribs the entire surface is marked by ex- 

 ceedingly fine, regular, concentric striae. The shell substance is 

 apparently very thin. 



Remarks. Whitfield is in error in his identification of Peclen 

 tenuitestus Gabb, as has been shown by a study of the type speci- 

 mens in the collection of the Philadelphia Academy of Science, 

 the species being described as a new form by him under the name 

 P. planicostatus. The shells which Whitfield has referred to P. 

 tenuitestus are quite a distinct form, however, and will need to 

 receive a new name as they are apparently undescribed; this 

 species is called P. whitfieldi in the present report. The true 

 P. tenuitestus differs from P. whitfieldi in its rnore nearly sub- 

 circular outline, the less compressed auriculations, the non-nodose 

 radiating ribs, and in the character of the fine concentric striae. 



Formation and locality. Navesink marl, near Freehold (133), 

 Crosswicks Creek (i47 4 , 149), near Marlboro (Whitfield). 



Geographic distribution. New Jersey. 



Pecten whitfieldi n. sp. 

 Plate L., Fig. 14. 



1886. Pecten tenuitestm Whitfield, Pal. N. J., vol. I (Monog. 

 U. S. G. S., vol. 9), p. 47, pi. 7, figs. 5-6. 



Description. Shell, exclusive of the auriculations, broadly 

 ovate in outline, higher than wide, the dimensions of a left valve 

 being: height, 40 mm.; width, 35 mm.; convexity, 5 mm.; 

 length of hinge-line about 16 mm. Left valve depressed con- 

 vex, deepest above the middle, the beak pointed, auriculations 



