CEPHALOPODA 01* THE CtiETACEOUS MARLS. 249 



AMMONITID^. 



Genus AMMONITES Brug. 



Ammonites complexus. 



Plate XLi, Figs. 5-7. 



Ammonites complexus Hall and Meek: Mem. Am. Acad. Arts and Sci., Boston, 

 new ser., vol. 5, p. 394, PI. iv, Fig. 1; Gabb, Synopsis, p. 9; Meek, Check 

 List, p. 24; Geol. Surv. New Jersey, 1868, p. 730; Invert. Paleont., U. S. 

 Geol. Surv. Terr., vol. 9, p. 447, PI. xxiv, Fig. 1. 



A single fragment only of this species has so far been recognized from 

 New Jersey. It consists of less than an inch in length of a volution having 

 a less diameter than the original specimen figured by Messrs. Hall and Meek; 

 biit it appears to have had a somewhat greater curvature, and consequently 

 has the appearance of having been a somewhat larger shell, though from 

 this imperfect fragment it would be difficult to say positively that such was 

 the case. The volutions were nearly circular in section and strongly em- 

 bracing, nearly one-third of the outer one having overlapped the inner one. 

 It has been crossed by low, rounded, transverse ridges, and broad, shallow 

 furrows, without nodes; the ridges becoming almost obsolete on the central 

 line of the back. Septa extremely complex and very closely arranged; so 

 closely that the branches of one septum interferes with and overlaps the one 

 behind it, so as to make it extremely difficult to trace the division of any 

 one septum even as far as the fragment preserves them. The extremities 

 of the digitations are slender and quite mucronate, presenting almost the 

 same features as those of Placenticeras tilifer. In this respect it differs from 

 all other species yet observed in the New Jersey formations except that 

 one. The dorsal lobe is more than half an inch long, and only slightly 

 divided below on the median line; the main divisions are separated each 

 into three compound divisions, each of which has many mucronate points; 

 above this there is one principal digitation on each side which has three 

 terminal points, and one or two farther up on each side. The first lateral 

 lobe has three terminal compound divisionSj with one smaller division on 

 each side above, and a minor one still higher. The second lateral lobe is 



