828 CRETACEOUS PALEONTOLOGY. 



tions of both lobes and saddles are more or less deeply bifid or 

 trifid. 



Remarks. This species is the common Scaphite of the Mer- 

 chantville clay. It is different from all other American 

 representatives of the genus in the peculiar expansion of the 

 living chamber to the geniculate bend beyond which it rapidly 

 contracts to the aperture. Whitfield's 5. similis is evidently only 

 a young individual of S. hippocrepis. 



Formation and locality. Merchantville clay, near Matawan 

 (101), near Jamesburg (139), Lenola (163). 



Sub-order PACHYCAMPYLL 

 Family SPHBNODISOIDAB. 

 Genus SPHENODISCUS Meek. 



Sphenodiscus lobatus (Tuomey). 

 Plate CVL, Figs. 1-2. 



1854. Ammonites lobata Tuomey, Proc. Acad. Nat. Sci. Phil. r 



vol. 7, p. 1 68. 

 1861. Ammonites lobata Gabb, Synop. Moll. Cret. Form., p, 



69 (13). 

 1864. Ammonites lobatus Meek, Check List Inv. Foss. N. A., 



Cret. and Jur., p. 24. 



1868. Ammonites lobatus Con., Cook's Geol. N. J., p. 730. 

 1892. Ammonites (Sphenodiscus) lenticularis Whitf., Pal. N, 



J{, vol. 2 (Monog. U. S. G. S., vol. 18), p. 258, pi. 41, 



figs. 8-9. 

 1903. Sphenodiscus lobatu\s Hyatt, Monog. U. S. G. S., vol. 44,. 



p. 66, pi. 6, figs. 1-2, pi. 7, figs. 1-2 pi. 9, figs. 11-13. 



Description. Shell attaining a large size, large examples 

 having a diameter of 220 mm. or more; compressed-lenticular in 

 form, the outer volutions almost completely embracing the inner, 

 leaving but a small or nearly closed umbilicus ; the sides of the 

 volutions smooth, gently convex from the umbilical to the ven- 



