DR. MANTELL ON BELEMNITES, ETC. 
175 
nacreous shelly covering cracked to pieces, and flaked off" from the clay : the illus- 
trative examples presently to be described, were preserved by imbuing them with 
a thick solution of gum, and allowing them to dry, before attempting to dig them 
up. From a great number of specimens I have selected four (Plate XIII. figs. 1, 
2, 3, 5.) in illustration of the form and structure of the phragmocone of the Belem- 
noteuthis. Figs. 2, and 3, exhibit, as I believe, the perfect shell, with the peristome, 
or mouth of the large anterior or basal chamber, entire. Although both these fossils 
are much compressed, the cavity of the receptacle filled with clay is distinctly seen 
in fig. 2 : in fig. 3, the margin of the peristome (a) is only visible on one side, owing to 
the position of the shell in the clay. In both specitnens the distal extremity is perfect; 
it terminates in a blunt point, having a longitudinal ridge on the side exposed, which 
probably indicates the dorsal aspect : in other instances, the corresponding space on 
the opposite or ventral side is occupied by two elevated, flat, slightly divergent lon- 
gitudinal bands, as in Plate XIII. fig. 5 ; in fig. 2, the thick corneo-calcareous 
epidermis covers the lower part of the cone, but is in a great measure removed from 
the upper portion, and the pearly or nacreous layer of shell which lies beneath is 
exposed. The epidermis in fig. 3, though much cracked by pressure, extends over 
the greater part of the shell. 
The descriptions of the phragmocone of the Belemnoteuthis, as given by Mr. 
Channing Pearce and Mr. Cunnington, accord in every respect with my own obser- 
vations. Mr. Cunnington particularly dwells on the constant and uniform occur- 
rence of the two strongly-marked ridges which extend upwards from the apex in a 
nearly parallel direction. “ These,” he observes, “ are shown in Plate II. fig. 6. of 
Professor Owen’s paper, and are regarded by that gentleman as resulting from the 
accidental crushing of the shell. I have, however, before me thirteen specimens, 
in which these ridges, though in some instances displaced by the compression they 
have undergone, are yet so distinct, and so constantly exhibit the same relative pro- 
portions and distances, that it is impossible not to regard them as resulting from 
original structure. A transverse section shows that these ridges are formed by an 
elongation of the fibres, and consequent thickening of the shell. Moreover, they are 
always exceedingly distinct in those specimens where the apex is solid — as is some- 
times the case to the extent of half an inch — and has resisted the force that has 
compressed the rest of the shell. It is obvious that this structure could never have 
fitted into the circular cavity constituting the alveolus of the Belenmite*." My son long 
since pointed out to me the marked difference in the form of the respective shells ; 
that of the Belemnite being an elongated cone (Plate XV. figs. 4, 5, h), and that of 
the Belemnoteuthis more obtuse (Plate XIII. figs. 4, 5) ; and he remarked that no 
amount of pressure could reduce the former into the same angle as the latter. 
[In the cabinet of the late Mr. Channing Pearce, there is a portion of a phragmo- 
cone of a Belemnoteuthis which is less compressed than any other specimen I have 
* London Geological Journal, pp. 98, 99. 
