CRETACEOUS TEKIOD. 201 



about every fourth or fifth costa is much more prominent and sharper than 

 the otiiers and extends quite across to the umbihcal side, wliile those between 

 die out or coalesce with tlie others at various distances. 



"Length, 1.45 inches; height, about 1.22 inches; breadth, 0.57 inch." 



Family AMMONITID^. 



Genus AMMONITES Bniguiere, 1789. 



Ammonites Loevianus White. 

 Plate XIX, fig. 1 a and h. 



Shell moderately large, robust ; volutions four or more, increasing rap- 

 idly in size, especially the outer one, so that the umbilicus is rather deep 

 but yet showing all the volutions ; each volution embracing between one- 

 quarter and one-third of the width of each preceding one ; transverse sec- 

 tion of outer volution, between the nodes, oval-subquadi-ate ; surface, upon 

 each side, marked by a row of moderately-elevated, transversely elongate 

 nodes, situated about one-third of the distance from the umbilicus to the 

 dorsum ; and also by a row of very prominent nodes on each side of the 

 dorsum. Each of these rows consist of the same number of nodes. The 

 dorsal nodes diverge strongly, but are wholly embraced by each succeeding 

 volution, and do not therefore appear in the umbilicus. Between these two 

 rows of dorsal nodes, the dorsum is slightly convex and'the outer surface of 

 the shell appears to have been marked by a small median carina. Between 

 these nodes and the umbilicus, the sides of the volution are broadly convex. 



A greater transverse elongation of the lateral nodes than exists on our 

 example would make each continuous with its corresponding dorsal node, 

 which would give to each lateral pair- of nodes the character of a rib. It is 

 not improbable that this modification may be found to exist in some ex- 

 amples of the species. 



Septa complex ; dorsal lobe and part of dorsal saddle unknown ; supe- 

 rior lateral lobe moderately large, bifid ; lateral saddle about as large as the 

 lateral lobe, but not bifid ; inferior lateral lobe small, naiTow, not bifid ; 

 accessory lobes and saddles few and small ; the borders of all the lobes and 

 saddles more or less deeply notched or dentate. 



