DR. MANTELL ON BELEMNITES, ETC. 
181 
PLATE XV. 
Fig. I. The guard or osselet of a Belemnite {B. attenuatus) invested by the perios- 
tricum, or external shelly capsule, c', c', d. 
a. Part of the chambered phragmocone seen in the alveolus. 
Fig. II. Another example of B. attenuatus, on which a large portion of the capsule 
remains, d, d. 
Fig. III. Exhibits the most considerable part of the structure of the Belemnite hitherto 
discovered. The original is twenty-two inches in length. 
a, a. Remains of the basal portion of the shelly phragmocone ; the apical 
chambered extremity is concealed by the investing capsule and 
guard, c, c. 
h, h. Two shelly processes proceeding from the margin of the peristome. 
c, d, d'. The capsule partially investing the guard (at d), and extending up- 
wards conceals at c, c, c, the siphonated part of the phragmocone, 
and expands into the horny receptacle (c"), within which the 
peristomal processes {b, V) are contained. 
A layer of dark brown animal matter extends from within the 
outline of the capsule at c", under the processes of the peristome ; 
and is probably the remains of the soft parts that occupied the 
interval between the receptacle and the phragmocone. The 
band on the left of the process b, presents a fibrous structure 
{d, d), and is marked with oblique lines, as if it were part of the 
muscular tunic or mantle. 
Fig. IV. The alveolar part of the guard of a Belemnite split open longitudinally to 
show the apical chambered portion of the phragmocone {a), with the shell 
perfect, and imbedded in the alveolus. The phragmocone terminates in a very- 
fine point, and is unsymmetrical ; inclining considerably to one side, in 
consequence of the position of the axis of the guard (c). A comparison of 
this figure with figs. 2, 3, 5, Plate XIII., will at once enable the observer to 
perceive how essentially the phragmocone of the Belemnite differs from 
that of the Belemnoteuthis. 
b. The radiated fractured surface of the spathose substance of the guard. 
Fig. V. The same fossil, with the phragmocone partially divested of the outer shell, 
to display the edges of the transverse septa. I have never seen in the 
Oxford Clay, the apical part of the phragmocone of a Belemnite detached 
from the alveolus. 
2b2 
