176 
DR. MANTELL ON BELEMNITES, ETC. 
seen, and is also the only instance in which the true external surface of the epidermis 
is preserved. Through the kindness of Mr. Charlesworth I have been favoured by 
Mr. Pearce, Senior, with the loan of this fossil, which is represented in Plate XIII. 
fig. 1. The external pellicle, though cracked, is almost entire, but is removed in a 
few places (a, a, a), so as to expose the brown corneo-calcareous layer which in most 
specimens appears as the outer case, as in Plate XIII. figs. 2, 3. The surface is very 
finely striated with delicate interrupted elevated lines, disposed in a longitudinal 
direction, as shown in the slightly enlarged drawing of part of the same at fig. 1 a. 
This structure appears to be analogous to that observable on the back of the sepio- 
staire of the Cuttle-fish, and on the guards of certain species of Belemnites ; but I have 
never observed any traces of such a texture on the surface of the phragmocones of 
the latter, which invariably presents the characters delineated in Plate XV. fig. 4, a.]* 
According to the facts at present known, the chambered cone of the Belemno- 
teuthis appears to me to approximate most nearly to the Beloptera-f, which has a 
horny calcareous conical shell with transverse septa, and is destitute of a guard. 
The Belemnite, — To avoid unnecessary details, I beg to refer to Dr. Buckland’s 
Bridgewater Essay :|:, Professor Owen’s Hunterian Lectures §, and my Medals of 
Creation II, for descriptions and figures of the form and structure of the Belemnite as 
indicated by the specimens then known ; and I now proceed to describe the most 
illustrative example from Trowbridge, which is represented (somewhat less than half 
the size of the original) in Plate XV. fig. 3. This fossil comprises the following 
parts : — 
1. The Capsule^ or periostricum ; this external investment (c', c', c'), which consists 
of a thin shelly or corneo-calcareous integument that closely embraces the guard, and 
gradually enlarging upwards, finally surrounds the peristome of the phragmocone, 
constituting the thin horny laminated sheath or receptacle (c, c), has been described 
by all previous observers as an extension of what they termed the sheath or capsule ; 
within this receptacle the ink-bag and other viscera were probably contained. 
2. The Guard or Osselet (Plate XV, figs. 1, 2), which is the fossil known to collectors 
as the Belemnite. This is an elongated conical body, of a fibro-calcareous spathose 
structure, diminishing in size towards its distal extremity, and terminating in a point. 
At the basal, or opposite end, it is truncated, and has a deep conical cavity termed 
the alveolus, which contains the siphonated apical portion of the phragmocone. 
3. The Phragmocone (Plate XV, figs. 3, 4, 5, a, a) : this is a thin shelly inverted cone ; 
the distal part containing a series of from twenty to thirty air-chambers or cells, 
* Received March 16, 1848. — S. H. C. 
t See Dr. Buckland’s Bridgewater Essay, Plate 44', fig. 15. 
I Ibid. Section VII. p. 371. § Vol. i. p. 333. || Vol. ii. p. 462. 
^ I would restrict the term sheath, or capsule, to this outer corneo-calcareous case or integument, for the 
phragmocone cannot properly he said to have a capsule, its conical shell being inseparably connected with 
the transverse septa ; it would be quite as correct to designate the involuted part of the shell of a Nautilus by 
this term, as the conical shell of the phragmocone of a Belemnite. 
