126 PALEONTOLOGY OF NEW JERSEY. 
14 inches by a height of about 14 imches. The species differs from G. 
petrosa in its greater size, more robust volutions, which are not so much flat- 
tened on the upper half, thereby giving a rounder and less oblique form, 
The wnbilicus is also larger in proportion and the shell more angular on its 
lower margin. = It differs from G. abysstius Morton in bemg less erect or 
more oblique, and in the angularity of the margin of the umbilicus. 
Formation and locality: It is found in the Lower Marls near Burlington, 
and at Mullica Hill, New Jersey. 
GYRODES CRENATA. 
Plate xv1, Figs. 4, 6. 
Natica (Gyrodes) crenata Conrad: Jour. Acad. Nat. Sci., Phila., 2d ser., vol. 4. 
p. 289. _ 
Gyrodes crenata (Conrad) Gabb: Synopsis, p. 60; Meek, Check List Cret. and Jur. 
Foss., p. 21. 
Shell below a medium size, broadly patulose in form, with a depressed 
spire and a very broad open umbilicus; volutions four or five, obliquely 
spreading and subangular below; inner whorls scarcely raised above the 
outer one, but very perceptibly distinct from the effects of a band of elevated 
crenulations or transverse nodes which marks the top of the volutions just 
below the suture line and forms a very decided ridge around the spiral por- 
tion of the shell, rendering the different volutions easily distinguishable; 
the broad umbilicus, limited below by a narrow, elevated, rounded ridge at 
the base of the volution, is also marked within by a less distinct carina 
a little below the middle of its depth; aperture oblique, truncated above by 
the flattening of the volution between the suture and the line of nodes 
which marks the volutions, and somewhat angular below; the angulation 
corresponding to the position of the rounded carina-like ridge at the base 
of the volution; surface of the shell marked by fine lines of growth corre- 
sponding to the margin of the apertare and passing over the line of nodes 
on the upper surface of the volution. 
The specimens of this species which [ have seen do not exceed seven- 
eighths of an inch in their greatest diameter, and all are more or less dis- 
torted by pressure. They closely resemble in form G. petrosa Morton, but 
