338 LECTURE XXIII. 



a great proportion of the muscular parts of the mantle, and the 

 remains of two lateral fins, the ink-bladder and duct, and a con- 

 siderable portion of the chambered cone. The two fins (Jig. iS3. 

 /, /) present the form of flattened transversely striated fibrous 

 masses with their free border entire and rounded. They are situ- 

 ated on each side of the visceral cavity, and demonstrate the ac- 

 curacy of M. Duval's objection to their position in the previous con- 

 jectural restorations. A large tract of the grey fibrous substance, 

 running parallel with and to one side of the remains of the head, 

 indicates the position of the infundibulum, and is terminated by a 

 concave truncation. At the middle of the visceral mass at the 

 interval of the two lateral fins, there lies a compressed body of a 

 horny texture and somewhat bilobed form, on which may be clearly 

 distinguished striae passing outwards in opposite directions from a 

 middle line, and diverging from each other in their course, which 

 resembles that of the fibres of the digastric muscle in the gizzards of 

 the Cephalopods : this apparent remnant of the stomach lies anterior 

 to the ink -bladder. There is a strong negative evidence that the 

 Belemnite possessed horny mandibles like the other naked Cepha- 

 lopods, since no calcareous ones or Rhyncholites have been dis- 

 covered associated with these remains. The cephalic arms, which 

 are preserved, belong to the normal series, and were eight in number : 

 they were provided, not with simple acetabula, but with a double 

 alternate series of slender elongated horny hooks, as in the genus of 

 existing Calamaries, called Onyclioteuthis* Each arm seems to have 

 been provided with from twelve to twenty pairs of these hooks. They 

 were doubtless developments of the horny hoop which encircles the 

 central process of the acetabulum, as in the modern Onychoteuthides ; 

 but in the position of the pallial fins, the Belemnite resembled the 

 Sepiola. The traces of the superadded pair of tentacula are some- 

 what doubtful. 



The modern decapodous Cephalopod, which most nearly resem- 

 bles the Belemnite in the structure of its internal shell, is the Sepia, 

 or common cuttle-fish ; the lateral fins of this species extend from 

 the apex to near the base of the mantle. The nucleus, or terminal 

 spine of the cuttlebone corresponds with the spathose guard of the 

 Belemnite : the convex posterior broad layer of friable calcareous and 

 horny matter is analogous to the enveloping cone ; but its margins, 

 instead of being approximated and soldered together, are free and 

 lateral in position : the successive plates, embedded in its concavity, 

 answer to the camerated cone of the Belemnite ; but, instead of 

 being perforated by one or many siphons, they are connected with 

 each other by a series of minute undulating lamellae. 



