828 CLASS = XIII. 
Baculites Lam. Shell straight, conical. 
Sp. Baculites Faujasti Lam., Fausas DE St Fonp Hist. nat. de la mont de 
St Pierre, Pl. 21, figs. 2, 3. QUENSTEDT unites with this Baculites anceps 
Lam. and Baculites vertebralis Bronn, Leth. geogn. Tab. xxxuit. fig. 6. 
These and Baculites neocomiensis D’ORB. are species from the chalk-for- 
mations, Baculites acuarius QUENSTEDT, Tab. 21, fig. 15, is hitherto the only 
known species from the Jwra-formation. 
B. Dibranchiata. 
In this division of Cephalopods, to which most of the species now 
living belong, the funnel is closed below. There is an organ for the 
secretion of a black fluid, which the animal can eject through the fun- 
nel, the irk-sac. In the genus Octopus this ink-sac is enclosed within 
the liver, but in the rest is remote from it. The colouring matter of 
some species is used as a paint, Sepia. Since some observations have 
indicated the presence of an ink-sac in the fossil Lelemmnites', it may 
probably be concluded, with Owen, that these petrifactions are in- 
ternal shells of Cephalopoda dibranchiata, which conclusion has, in 
fact, been since established by the observation of petrified animals’. 
Family XIII. Decacera s. Sepiacea. Arms ten, two longer 
than the rest, round. 
Belemnites BrEYN, LAM. Shell fossil, conical, including inter- 
nally a multilocular, shorter portion (alveolttes). 
Belemnites or dart-stones ; thus named on account of their dart-like form. 
These petrifactions are found abundantly in the secondary mountains of 
the oolite and chalk-periods. Compare, amongst others, DucRoTAY DBE 
BuAInviIttE Mém. sur les Belemnites, Paris, 1827, 4to; J. S. Minuer 
Observations on Belemn., Transact. of the Geol. Soc. of London, sec. Series, 
11. 1829, pp. 43—62, Pl. 6—g; Bronn Leth. geogn. pp. 402—418, pp. 
714—720. 
Spirula Lam. Animal with ten tentacles, two longer. Shell 
placed in the posterior part of animal, thin, spiral, with wreaths 
not contiguous. Partitions concave, perforated by siphon at the 
inside. 
1 AGcassiz in V. LEONHARD u. BRronn Neues Jahrb. fiir Mineralogie, Geognosie u. 
Geol. 1835, s. 163, BuckLanD Geology and Mineralogy, London, 1836, 8vo, (Bridge- 
water Treatises, VI.) p. 374, Pl. 44’, fig. 7, Pl. 44°’. 
2 Lectures on the comp. Anat. and Physiol, of invertebrate Animals, p. 337, 2nd ed. 
pp- 597—603. 
