24. EOCENE MOLLUSCA. 
Parisiensis, he confounded with it the remains in question. M. Voltz was the first to 
examine these remains with the attention they deserve. This author instituted a com- 
parison between the shell of the Beloptera Belemnitoidea, that of the Beloptera Sepioidea 
(Sepia Parisiensis), and the recent Sepzon, and stated the reasons which induced him to 
consider the Beloptera Sepioidea as belonging to a distinct genus, equally removed from 
the Beloptera Belemnitoidea and the recent Sepia, and as forming a natural connexion 
between Belemnites and Sepia; and he proposed the present genus, Belosepia, for 
its reception. The principal ground advanced by him to justify this separation was, 
that the remains of Belosepia indicated a camerated and siphoniferous structure in the 
contents of the sheath, widely different from that of the Sepion ; and, if this opinion 
be correct, there cannot be a doubt as to the propriety of the separation. M. Deshayes, 
however, in his ‘ Description des Coquilles fossiles des Environs de Paris, without 
questioning in any respect the accuracy of M. Voltz’s description, without referring 
even to that author’s opinion as to the siphoniferous structure of the shell, but 
simply relying on the analogy drawn from the general resemblance between the 
remains of the Sepza Parisiensis and the Sepion, unhesitatingly rejected the genus 
Belosepia as not possessing characters sufficiently distinct from those of Sepia; 
although he considered that it would be desirable to form a section in the genus Sepia 
for the reception of the fossil species. In this opmion M. Deshayes has been followed 
by MM. Pictet and d’Orbigny. I cannot concur with these authors in the rejection of 
M. Voltz’s genus. The Belosepion®™ appears to me to present peculiarities of structure, 
indicating corresponding important zoological differences, which render it impossible 
to regard the animal to which it belonged as forming part of the existing genus Sepia. 
The Belosepion, like the internal shell of the Sepia, is a compound shell, and 
consists of—Ist, a solid calcareous mucro, or rostrum, commonly called the beak, 
inflected at the posterior extremity towards the dorsal aspect, and at the base ex- 
panding on the dorsal aspect into an elevated, compressed, and more or less rugose 
mass, called by M. Deshayes the ca//vs, and on the ventral aspect into a thick semi- 
circular plate, bent outwards, in a radiated fold, over, but not touching, the upper 
portion of the rostrum, denticulated on the margin, and continued laterally into the 
parietes of the sheath. 
2d. An inverted semiconical calcareous plate, termed the sheath, externally coarsely 
granulated, internally smooth, but presenting a series of undulating impressions, con- 
verging towards the inverted apex, where the sheath terminates in a conical cavity, 
formed in the anterior portion of the rostrum, and strongly inflected towards the 
ventral aspect, so that the posterior extremity presses against the origin of the radiated 
fold. 
* The term Belosepion is used here to describe the entire internal shell of the Belosepia ; in the same 
way as the term Sepion (Sepiostaire of De Blainville) is used by English writers to describe the internal 
shell of the Sepia, or what is usually known as “ Cuttlefish-bone.” 
