[ 8 °4 ] 
thoceratitas ; nay, I have feen fome in Dr. Mafon’s 
private collection at Cambridge, which he told me 
were found in England, and, I think, came from 
"Whitby; the character of which being exactly the 
fame with the nautili, I make no fcruple to clafs 
them together. 
Whofoever will examine nicely bodies of any ge- 
nera, will have a difficulty to fay, where they begin, 
and where they end ; the gradation is fo infenfible, 
that they mull be bewilder’d. 
From the orthoceratitas, which is undoubtedly a 
fpecies of nautilus, we gradually proceed to the be- 
lemnites. The orthoceratites is a flrait concamerated 
ffiell, ending in a point ; fome of which I have feen 
in ftone eighteen inches long; fee Fig. 2, 3, 4, 5, 
and 12. 
The nucleus, or alveolus, of the belemnites is like- 
wife a flrait concamerated fhell or body, exactly 
refembling the other in ffiape and flruCture, but of a 
fmaller fpecies, Fig. 6 and 10 ; and, I think, from 
the very great analogy, may reafonably be deemed to 
be of the fame family. 
In the conic cavity of the belemnites, Fig. 7. that 
contains the nucleus, it is very common to oblerve 
vifible marks of a ffielly fubflance, as a farther con- 
firmation that the nucleus was a teflaceous body. 
And now a word as to the belemnites itfelf, the 
counter-part to the other. 
It has indeed been truly matter of fpeculation, 
how that huge folid fubflance called the belemnites, 
exclulive of the nucleus, could be formed ; and how 
it happens that fome ffiould have the nucleus within 
them, others not ; the cavity to contain the fame in 
fome 
