iiELEMNITE COMPARED WITH NAUTILUS. o77 
Comparing the shell of Belemnite, with that 
’^f Nautilus, we find the agreement of all their 
'e absence of the nacreous horny sheath, by supposing that a 
'condition of the matrix favourable to tlie preservation of the 
careous sheath was unfavourable to the preservation of horny 
j^embrane ; and we may also explain the absence of ink-bags, 
y supposing that the decomposition of the soft parts of the 
^‘^•nial usually caused the ink to be dispersed, before the body 
"'as buried in the earthy sediment then going on. 
the base of Golden Cap hill, near Charmouth, the shore 
Pfescnts two strata of marl almost paved with Belemnites, and 
®t:parated by about three feet only of comparatively barren marl. 
® great numbers of these Belemnites have Serpulm, and other 
®^traneous shells attached to them, we learn from this circum- 
^ance that the bodies and ink-bags had decomposed, and the 
® eninites lain some time uncovered at the bottom. These 
^ s are explained by supposing that the sea near this spot was 
Belemno-sepiso during the intervals of the 
stat°**^*°” the Lias. Similar conclusions follow, from the 
e of many Belemnites in the chalk of Antrim, which had 
hotf *^y boring animals, whilst they lay at the 
ch W ^ perforations filled with casts of 
^ or flint, when the matter of the chalk strata was deposited 
'Pon them, in a soft and fluid state. (See Allan’s Paper on 
“elemnite, Trans. Royal Soc. Edin., and Miller’s Paper, Geol. 
trans. Lond. 1826, p. 53.) 
^^Thus of the millions of Belemnites which crowd the Secondary 
^ormations, only the fibro-calcareous sheath and chambered al- 
she preserved; whilst in certain shale beds this 
1 o^ath and shell have sometimes entirely disappeared, and the 
p rny or nacreous sheath and ink-bag alone ren)ain. See PI. 44", 
C 8. In the rare case, PI. 44', Fig. 7, 
afforded the clue to this liilherto unexplained eiiiginay 
111 ■ three essential parts of a Belemnite preserved in 
"’itli" places nearly entire. The ink-bag (c) is placed 
alv 'ai'terior horny cup (e, e', e") ; aud the chambered 
ca^^ within the hollow cone of the posterior fibro 
^areous shell, or common Belemnite. 
