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 its 

 inner edge, of a preceding whorl ; the edges of the 

 nearly flat front project a little, so that it appears con- 

 cave ; the other 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 



