836 CRETACEOUS PALEONTOLOGY. 



Formation and locality. Marshalltown clay-marl, near 

 Swedesboro (177); Wenonah sand, near Marlboro (I3O 1 ); 

 Navesink marl, Navesink Hills (Whitfield, type specimen). 



Geographic distribution. New Jersey. 



Family MAMMITIDAE. 



Genus BARROISICERAS Gross. 



Barroisiceras dentato-carinatus (Rcemer). 



Plate CL, Figs. 5-6. 



1849. Ammonites dentato-carinatus Roem., Texas, p. 417. 

 1852. Ammonites dentato-carinatus Roem., Kreid. von Texas, 



P- 33, Pi- i, % s - 2 a ~ c - 

 1861. Ammonites dentato-carinatus Gabb, Synop. Moll. Cret. 



Form., p. 65 (9). 

 1864. Ammonites dentato-carinatus Meek, Check List Inv. 



Foss. N. A., Cret and Jur., p. 24. 

 1892. Ammonites dentato-carinatus Whitf., Pal. N. J., vol. 2 



(Monog. U. S. G. S., vol. 18), p. 250, pi. 41, figs. 3-4. 

 1905. Ammonites dentatocarinatus Johns., Proc. Acad. Nat. 



Sci. Phil., 1905, p. 27. 



fr~ . . 



Description. "The shell when entire has been compressed dis- 

 coidal, with a proportionally small umbilicus, the volutions have 

 been sharp on the ventral edge and marked by a series of undu- 

 lations which gave rise to the specific name. The sides are 

 ornamented by two lines of nodes which divide the surface into 

 three nearly equal spaces, also by transverse ridges which are 

 low and rounded, and pass from the margin of the umbilicus 

 almost directly across the volutions to a node one-third of its 

 breadth from the margin, and are then bent sharply forward, 

 their convexity giving rise to the undulations on the dorsal cari- 

 nation. Some of the ridges bifurcate at the inner line of nodes, 

 each branch reaching the margin as independent ridges, but the 

 fragment is too small to show how frequently this feature 

 occurs." (Whitfield.) 



