matter, similar to that we find on certain internal membranes of many fishes.[1]
- ↑ I would here add a few words in explanation of the curious fact, that among the innumerable specimens of Belemnites which have so long attracted the attention of naturalists, not one has till now been found entire in all its parts, having the ink within its external chamber; either the 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 from the condition of the 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 capacity for preserving 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 happens 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 condition of the matrix favourable to the preservation of the calcareous sheath 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 the 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 Serpulæ, 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 the sea near this spot was much frequented by Belemno-sepiæ during the intervals of the deposition of the Lias. Similar 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 tilled with casts of chalk or flint, when the matter of the chalk
