MOLLUSCA. 381 



field (183, 165); Wenonah sand, near Marlboro (130); Red 

 Bank sand, Red Bank (116), Shrewsbury river (119), near 

 Middletown (112) ; Tinton beds, Beers Hill cut, south of Key- 

 port (I29 5 ). 



Geographic distribution. New Jersey. 



Genus YOUDIA Moller. 



Yoldia longifrons (Conrad). 

 Plate XXX., Fig. 5. 



1860. Leda longifrons Con., Jour. Acad. Nat. Sci. Phil., 2d 



ser., vol. 4, p. 281, pi. 46, fig. 18. 



1861. L<eda longifrons Gabb, Synop. Moll. Cret. Form., p. 189 



(133). 

 1864. Nuculana longifrons Meek, Check List Inv. Foss. N. A., 



Cret. and Jur., p. 8. 

 1886. Nucwlana longifrons Whitf., Pal. N. J., vol. i (Monog. 



U. S. G. S., vol. 9), p. 107, pi. n, figs. 16-17. 

 1905. Yoldia longifrons Johns., Proc. Acad. Nat Sci. Phil. 



(1905), p. 8, 



Description. The dimensions of an average specimen are: 

 length, 36 mm. ; height, 14.5 mm. ; convexity, 4.5 mm. Shell 

 longitudinally subelliptical in outline, a little narrower behind 

 than in front. Beaks scarcely elevated above the hinge-line, 

 situated about two-fifths the length of the shell from the ante- 

 rior extremity. Anterior and posterior cardinal margins slop- 

 ing away from the beak on either side, meeting in an angle of 

 150 to 155 ; anterior margin broadly rounded, its most anterior 

 extension above the mid-height of the shell; posterior margin 

 more narrowly rounded, its greatest extension above the middle ; 

 ventral margin gently convex in the middle, curving upward 

 more sharply at either end. Impression of the hinge-line in the 

 internal cast bearing about 35 or more < shaped teeth posteri- 

 orly in nearly a straight line, and about 25 /-shaped teeth an- 

 teriorly, also in a straight line. External surface of the shell 

 polished, marked only by fine, more or less conspicuous concen- 

 tric lines of growth. 



