81 
ORTHOCERA paradoxica. 
TAB. CCCCLVII. 
Spec. Char. Lanceolate, curved, three angled, 
with a flat front, and convex sides ; aper- 
ture an equilateral triangle ; siphuncle 
nearly central. 
Although this shell is called an Orthocera, it is in 
many particulars very different from any other known 
species, and approaches to a Nautilus by its curvature ; 
but there is no impression, or any other mark about it? 
inner edge, of a preceding whorl ; the edges of the 
nearly flat front project a little, so that it appears con- 
cave ; the othey sides are convex but not similar, the 
greatest curvature being near the inner edge upon one 
of them, and in the middle upon the other : if we can 
depend upon the indications of the specimen, the aper- 
ture has a deep sinus in the edge of each of its sides, and 
the front. 
It would perhaps have been proper to constitute a new 
genus of this very remarkable fossil, to be placed be- 
tween Nautilus and Orthocera, but experience has shewn 
us how dangerous it is to form genera from such charac- 
ters as fossils possess, especially when fragments only are 
preserved, and we have not the whole tribe before us. 
We know of only a short portion of the shell before us ; 
one end of it is but half as wide as the other, and the 
curvature not more than the sixth part of a circle ; 
therefore if it be an involute shell, the inner whorls must 
be very slender, or the outer one must have receded from 
them with a much less degree of curvature than they 
