CEPHALOPODA OF THE CRETACEOUS MARLS. 249 
AMMONITID. 
Genus AMMONITES Brug. 
AMMONITES COMPLEXUS. 
Plate xxi, Figs. 5-7. 
Ammonites complexus Hall and Meek: Mem. Am. Acad. Arts and Sci., Boston, 
new ser., vol. 5, p. 394, Pl. 1v, 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, Pl. 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; 
but 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 divisions, with one smaller division on 
each side above, and a minor one still higher. The second lateral lobe is 
