CEPHALOPODA OF THE EOCENE MARLS. 287 
Genus ATURIA Bronn. 
ATURIA VANUXEMI. 
Plate xLIx, Figs. 1, 3, and Plate L, Fig. 1. 
Pelaqus Vanuxemi Conrad: Jour. Acad. Nat. Sci., vol. 1, 2d ser., p. 130, Pl. xrv, 
Fig. 15. 
Aturia Vanuxemi Conrad: Am. Jour. Conch., vol. 2, p. 15. 
Aturia ziczac (Sow.) Conrad: Am. Jour. Conch., vol. 1, p. 150; Smithsonian 
Check List, p. 19. 
Nautilus angustatus Con.: Am. Jour. Conch., vol. 1, p. 150; not N. angustatus 
Conrad, U. 8. Expl. Exp. Geology, p. 728, Pl. xx, Figs. 5, 6. 
Shell of moderately large size, the most perfect one which I have seen, 
but which is an internal cast only, measures 64 inches in its longest diame- 
ter, and has a thickness from side to side of about 2 inches, but has appar- 
ently been considerably compressed in this direction. The form is closely 
convolute with a closed umbilicus; sides depressed, convex, and dorsum 
narrowly rounded. The inner volution projects into the aperture of the 
outer one about two-fifths of the distance from the umbilicus to the outer 
margin, leaving the aperture, in this laterally compressed specimen, some- 
what elongately halbert shaped. The septa are somewhat closely arranged 
and number about sixteen in the last coil of the shell. In rising from the 
umbilical depression they make a broad forward curve or arch, which 
extends to a little beyond the middle of the width of the volution, from 
which point they are bent abruptly backward, and form a proportionally 
long, narrow, and somewhat pointed spur, the outer edge of which is 
straighter than the inner and with that of those in the rear and in advance 
form a nearly straight and continuous line parallel to the margin of the 
dorsum. After this edge of the spur reaches a point about opposite the 
place of abrupt flexure of the inner side, the line runs straight across the 
back of the volution, forming a broad projecting lip on the back of the 
shell equal in length to that of the spur on the side of the volution. The 
spur on the side, rather outside of the middle of the volution, with the point 
reaching almost to the corner of the outer lip of the septum below, is a 
rather well marked feature and somewhat characteristic. Septa deeply con- 
cave, as seen in an apertural view. Siphon large, situated fully its own 
