284 INK-BAG. 



ous matter, similar to that we find on certain internal mem 

 branes of many fishes.* 



• I would here add a few words of explanation of the curious fact, that 

 among- the innumerable specimens of Belemnites wliicli have so long at- 

 tracted the attention of natui-alists, not one lias till now been found entire 

 in all its parts, having the ink within its external chamber; either tiie fibro- 

 calcareous sheath is found detached from the horny sheath and ink-bag, or 

 the ink-bag is found apart from the Belemnite, and surrounded only by 

 the nacreous horny membrane of its anterior chamber. We know fron> 

 the condition of tiie compressed nacreous Ammonites in the Lias-shale at 

 Watchet, that the nacreous lining only of these shells is here preserved, 

 whilst the shell itself has perished. This fact seems to explain the absence 

 of the calcareous sheath and shell in almost every specimen of ink-bags at 

 Lyme Regis, which is surrounded with iridescent nacre, like that of the 

 Ammonites of Watchet. The matrix in these cases may have had a capa- 

 city for presei"ving nacreous or horny substances, whilst it allowed the more 

 soluble calcareous matter of shells to be removed, probably dissolved in 

 some acid. 



The greater difficulty is to explain the reason, why amidst the millions 

 of Belemnites that are dispersed indiscriminately through almost all strata of 

 the Secondary series, and sometimes form entire pavements in beds of shale 

 connected with the Lias and Inferior oolite, it so rarely liappens that either 

 the horny-sheath, or the ink-bag, have been preserved. We may, I think, 

 explain the absence of the nacreous horny-sheath, by supposing that a con- 

 dition of the matrix favourable to the preservation of the calcareous slieath 

 was unfavourable to the preservation of horny membrane ; and we may also 

 explain the absence of ink-bags, by supposing that the decomposition of the 

 soft parts of the animal usually caused tlie ink to be dispersed, before the 

 body was buried in the earthy sediment then going on. 



At 'the base of Golden Cap hill, near Charmouth, the shore presents 

 two strata of marl almost paved with Belemnites, and separated by about 

 three feet only of comparatively barren marl. As great numbers of these 

 Belemnites have Surpulje, and other extraneous shells attached to them, we 

 learn from this circumstance that the bodies and ink-bags had decomposed, 

 and the Belemnites lain some time uncovered at the bottom. These facts 

 are explained by supposing that tlie sea near this spot was much frequented 

 by Belemno-sepise during the intervals of the deposition of the Lias. Simi- 

 lar conclusions follow, from the state of many Belemnites in the chalk of 

 Antrim, which had been perforated by small boring animals, whilst they 

 lay at the bottom of the sea, and these perforations filled with casts of chalk 



