40 EOCENE MOLLUSCA. 
The principal character, however, which distinguishes Belemnosis is the aperture 
forming a communication between the alveolar chambers and the sac in which the 
shell was lodged. In all the camerated siphoniferous shells, I believe without exception, 
the inferior extremity of the alveolus and phragmocone is perfectly closed, and the air- 
chambers have not any direct communication with the pallial sac; and, in fact, commu- 
nicate only with the pericardial cavity by means of the membranous siphuncle. Walch, 
it is true, in his ‘ Recueil de Monumens, &c.,’ figured a Belemnite, which he described as 
having a small circular hole at the extremity of a curved point; upon which figure, 
with embellishments of his own, De Montfort proposed the genus Paclites, referred to 
by Parkinson, and quoted by De Blainville. This genus, however, is universally 
rejected, as founded on characters merely accidental or imaginary. M. dOrbigny 
states, that in certain exceptional cases the extremities of the rostra of Belemnites, at 
the last period of their growth, form tubular prolongations, and that they are also lable 
to distortion from accident. The extreme points of the successive layers, which form 
the spathose guard, are apparently, in some instances, more susceptible of disintegration 
than the other parts, and thus tubular openings may be formed along what Voltz terms 
the apicial line. But in all these cases the pore is merely terminal, and does not 
extend far up the sheath. The structure found in el/emnosis, therefore, appears to 
be peculiar to it; and would indicate an application of the siphuncular function, 
whatever that function may be, different from that in all other siphoniferous shells, 
and suggests a corresponding peculiarity in the organization of the animal. 
From the absence of the elongated rostrum which characterises the Belosepia 
and Beloptere, we infer that the animal of Le/emnosis was not littoral in its habits, 
but existed in a comparatively deep sea; and the occurrence of the unique 
specimen, upon which the genus is founded, at Highgate, where the organic remains 
indicate a shallow-sea deposit, is attributable most probably to the casual drifting of 
the animal. 
No. 6. BrLemnosis pricata. ff. L. Hdwards. Tab. 2, fig. 3a—e. 
BELOPTERA ANOMALA; Sowerby. 1829. Min. Con. vol. vi, p. 183, tab. 591, fig. 2. 
— Morris. 1843. Cat. of Brit. Foss. p. 178. 
— — Pictet. 1845, Traité élement. de Paleont. tom. ii, p. 316. 
— — Deshayes. 1845-6. 2d Edit. de Hist. Naturelle, &c. par Lam. 
= — D Orbigny. 1845-7. Moll. viv. et foss. tom. i, p. 309, tab. 14, 
figs. 8-10. 
B. testdé oblongo-elongatd, supra convead, umbone obtusissimo, lateraliter compresso, 
et deorsum leviter inflecto terminatd: marginibus ventralibus antice depressis, postice 
sub-convevis, facies externas acutas, internas, oblique triplicatas, prebentibus: foramine 
umbonali circulari. 
