190 : DESCRIPTION OF SHELLS. 
MOLLUSCA CEPHALOPODA. 
DIsRANCHIATA. 
BrLosEPIAD&. 
The fossils which are arranged under this Order were noticed by Guettard in 
his ‘Mémoires,’ in 1783, among ‘‘ Glossopétres ou dents de Requins fossiles,” 
when after having called one a ‘‘ Dent ailée*,” and another ‘‘ Dent un peu 
courbe a base ailéet,” he asks, ‘‘ Ces corps sont-ils bien réellement des dents ?{” 
and adds, ‘‘ La seule facon de déterminer au juste leur nature est de trouver un 
poisson ou autre animal qui ait un corps semblable.”” This was sound reason- 
ing ; but it was left to Cuvier, after several erroneous indications by others, to 
point out the animal which did possess a body resembling them, and which he 
showed to be the Cuttle-fish or Sepia, in whose bone, or rather internal shell, a 
strong resemblance was immediately acknowledged ; they however form links 
between the Sepia and Belemnites, whose animal having been since discovered 
in the fossil state, confirms the affinity. 
Belosepia, Voltz. 
This genus, proposed by Voltz in 1830§ as distinct from Sepia, and adopted 
by Blainville, but rejected by Deshayes and his followers, appears notwithstand- 
ing to be a good genus; unfortunately only a small portion of the shell is ever 
found, which prevents a complete comparison being made between it and the 
bone or shell of Sepia ; enough however is known to show their affinity and also 
some good distinguishing marks. It may be convenient therefore to describe the 
shell or bone of the Cuttle-fish before defining the Belosepia. The shell of Sepia 
has for its basis a horny membrane, shaped like the elongated bowl of a spoon, 
and lined to near its edge with a thin layer of calcareous matter ; the pointed end 
being directed towards the head of the animal is consequently the anterior, and 
the concave surface is ventral; near the posterior end and at a small distance 
from the bottom of the concave surface is an obtuse transverse ridge, beneath 
which the cavity becomes pointed, forming a kind of pit ; from this pit proceeds 
a spongy convex mass that nearly fills the horny membrane ; it is composed of 
thin, curved, parallel plates directed longitudinally, and separated from each other 
* Vol. v. p. 184, pl. 2. f. 10, 11 & 12: this is Beloptera belemnitoidea. 
+ Ibid. p. 186, pl. 2. f. 23, 29 & 30, are Belosepic. { Ibid. p. 185. 
§ Mémoires sur les Belemnites, p. 23. 
