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ORTHOCERAo 
Gen. Char. Shell straight or slightly bent, fusi- 
form ; chambered, siphunculed ; margins of the 
septa even or with one or two gentle wavings. 
In what manner the shells of this Genus terminate at either 
end, is at present not well ascertained. The jointed alveoli 
of some Belemnites, particularly in such specimens as ex- 
hibit them continued beyond the more solid parts, very 
nearly resemble some of the specimens of Orthocera, but as 
yet I have seen none with a central siphunculus. I have 
very lately been permitted by the kindness of Sir Joseph 
Banks to sketch a large specimen, in which the chambered 
part or Alveolus extends about seven inches beyond the 
Belemnite, properly so called, and so nearly resembles my 
Orthocera conica, that I suspect it to be the same species 
larger*. 
We know of many species of Orthocera to which we 
have seen no Belemnite attached, and the proportions of 
which will match no Belemnite we are acquainted with. 
May it not be that the shell of some Orthocerae is so 
thin to the very point, as not to be recognized as a Belem- 
nite, and that there is a series from these to such as have 
the shell so thick and large as to be arranged as Belemnites 
alone? The discovery of an Orthocera with a thin shell 
perfect to the end, would go far towards answering this 
query. 
* I hope to receive more information upon this head, when I shall be 
happy in presenting the figure to my readers. 
