VOL. LI v.] PHILOSOPHICAL TRANSACTIONS. Qi 



larger, it forms a second cell or chamber b to c, at the same time covers the 

 first cell by forming the appendage or guard c, i, which is the first stage of the 

 beleranite. In forming the third cell c, d, fresh laminae or coverings are carried 

 on from d to k ; and so of the rest, e, f, g, h ; or I, m, n, o. "When we have 

 duly considered the manner in which the shell is thus formed ; it will be no 

 difficult task to account for the diflTerent sections and broken parts of the belem- 

 nite, and in what manner they were reduced to the several forms or appearances 

 in which we commonly find them. •" 



The better to illustrate his conjecture, Mr. P. first exhibits some drawings, 

 which show the several specimens broken and imperfect ; and then proposes his 

 sentiments concerning them before they were deserted by their inhabitants. 

 Fig. 6 shows the spine of the echinus ovarius broken obliquely, as is common 

 to all of them. Fig. 5 exhibits the inner structure of the belemnite, when 

 broken horizontally, with the central rays. Fig. 11 is the same belemnite split 

 through its axis. Fig. 12 and 13, are broken in the same direction as fig. 5 

 and 11, and show how the several laminae* are placed one over another, in the 

 manner in which it is formed. Fig. 1 4 shows the belemnite in the most perfect 

 state we ever find it. Fig. 4 is the fusiform belemnite found in chalk, which 

 has been often taken for a spine : a, which is the termination of the conical 

 cavity, has been thought to be the socket of the spine, which receives the 

 papilla, when growing to the echinus ; but, when compared with the socket of 

 the true spine (fig. 6, b) we find it widely different. The pricked lines b, c, b, c, 

 show what the fusiform belemnite was, when perfect, with the alveolus d, e. 

 Many of those found in chalk seem to be somewhat injured at the end a, where 

 tliey are deficient, and are rounded, but have an uneven surface, as if they had 

 been gnawed or eaten by the pholas. Those found in clay near Piddington, 

 (fig. 3,) Oxfordshire, approach nearer to the fusiform kind, and have a different 

 appearance at the smaller end f, where the laminae are reduced to a white im- 

 palpable powder, by corrosive juices in the earth, so as to stain the fingers when 

 first taken out ; and they afterwards retain a white chalky appearance : but, 

 among a great number^ he never found one that was 3 inches long. These 

 have suffered in the same manner as fig. 4. Fig. 3, f, shows where the alveolus 

 terminates : g, h. g, h, how much has been destroyed by vitriolic acids."|- At 



• These distinctions of the larcinse appear to be owing to the mineral steams insinuating them- 

 selves into the belemnite, when the spar pervaded the pores, and destroyed the texture, but retained 

 the true form by substituting itself, and filling the plasm or mould of the belemnite. — Orig. 



+ It may be asked, why one part suffers more than another, as all parts are homogeneous, and 

 firee from extraneous mixtures ? My answer is ; because those parts, where the concamerated shell 

 is lodged, are much thinner than the other parts of the belemnite ; and consequently the walls are 

 more easily broken down, and the alveolus, being still less solid, is sooner destroyed, and reduced 

 to an impalpable powder, by vitriolic and other acids, which the water takes up as it passes through 



