CEPHALOPODA. 39 
species but also the Beloptera anomala of Sowerby to the genus Beloptera, the 
principal character of which he states to be the association of a conical chambered 
cavity, similar to that of the Belemnites, with the beak (rostrum) of the Sepia. M. 
d’Orbigny also (Moll. viv. et foss.) refers to that genus the remains in question, which, 
he says, resemble Beloptera Levesquei in the absence of the lateral wings, but are 
distinguished from it as well by the want of the under part (the ventral paries) of the 
shell and of a distinct beak,.as by the air-chambers being apparent on the under side. 
These remains unquestionably bear a close affinity to Beloptera; but the peculiarities 
they present appear to me to separate them distinctly from that genus, and fully to 
justify the establishment of a new genus for their reception. 
The shell of Belemnosis consists of an elongated semiconical sheath, the apex 
of which expands into a short semicylindrical umbo, pierced on the ventral surface, 
and inflected towards the ventral aspect. The sheath is convex on the dorsal surface, 
and is without a ventral paries; the margins at the superior extremity are narrow, 
and present outwardly sharp edges, which extend rather more than one third of 
the length of the shell; as the margins approach the inferior extremity they expand, 
and the inner edges gradually become nearer to each other, until they unite immediately 
above the umbonal pore. The margins of the pore are elevated, and the pore itself 
penetrates to, and communicates with, the air-chambers. The septa are transverse 
and concave ; the presence of a siphuncle and its ventral position are indicated by 
angular inflections on the sutural impressions along the medial line of the ventral 
surface; the septa are contained in, and wholly enveloped by, a thin conical sheath, 
which also is covered by a second and somewhat thicker conical layer lodged in the 
outer sheath. 
The principal character of Be/optera, viz., the association of the elongated rostrum 
of the Sepion with the phragmocone of the Belemnite, fails in Belemnosis ; and the 
lateral expansions which, assuming their fullest development in Beloptera Belemnitoidea, 
still characterise B. Levesquei, although reduced in that species to prominent carinze, 
are here wanting, or, at the utmost, are but feebly represented by the sharp outer 
edges of the ventral margins of the sheath. In Be/optera, the outer cone, which 
contains the inner sheath and its contents, and which exactly corresponds with the 
phragmocone of the Belemnite, is entire; whereas, in elemnosis, the ventral paries 
is wanting, or very thin. In this respect Belemnosis presents an analogy with Belem- 
nitella (D’Orb.), a genus of the Belemnitidee, characterised by a fissure in the phrag- 
mocone communicating with the external paries of the alveolus. This peculiar form of 
Belemnite at present appears to be confined to the upper chalk formation, and it would 
seem to connect the true Belemnite with the present genus, in which the fissure be- 
comes largely expanded, resembling the wide cavity of Belosepia. Thus the transition 
from Belosepia, through Belemnosis and Belemnitella, into Belemnite will be easy and 
natural, and the chain of connexion between the latter genus and the recent Sepia will 
be complete. 
