Royal Society. (j 1 



the fossils of the Oxford clay, and other oolitic deposits cut through 

 or exposed hy the engineering operations. Among those transmitted 

 to the author are many illustrative examples of Belemnoteuthes and 

 Belemnites ; some of which confirm the opinions entertained hy the 

 late Mr. C. Pearce, Mr. Cunnington, and other competent observers, 

 that the body and soft parts, with the cephalic uncinated arms, &c. 

 of cephalopods, obtained from Christian-Malford by the Noble Pre- 

 sident and Mr. Pearce Pratt, and referred by Professor Owen in the 

 memoir above-mentioned to the Belemnite, belong to a distinct 

 genus — the Belemnoteuthis. 



The author describes and figures several perfect examples of the 

 phragmocone of the Belemnoteuthis, and institutes a comparison be- 

 tween them and a beautiful example of the phragmocone of a belem- 

 nite occupying the alveolus of the guard; and defines the essential dif- 

 ferences observable in the form and structure of these chambered cal- 

 careous cones. He especially points out as distinctive characters of 

 the phragmocone of the Belemnoteuthis, two flat longitudinal ridges 

 which extend upwards from the apical extremity, and the granulated 

 and striated external surface of the epidermis. The phragmocone 

 of the Belemnite has a smooth surface, is destitute of any lon- 

 gitudinal ridges, and terminates at the apex in a very fine point, the 

 axis being in an oblique direction. 



The author next describes a remarkable specimen of a Belemnite, 

 twenty- two inches in length, in which the osselet or guard, phrag- 

 mocone, and capsule or receptacle, are preserved in connexion. In 

 this fossil is demonstrated, for the first time, the upper or basal ter- 

 mination of the phragmocone, with two elongated calcareous pro- 

 cesses extending upwards from the margin : these are analogous in 

 form and position to the prolongations from the peristome of the 

 outer chamber of certain Ammonites, as for example, in A. Jasoni. 

 In the phragmocone of the Belemnoteuthis the peristome is entire. 



Another interesting part of the structure of the Belemnite, not 

 previously detected, is also shown in the same specimen, as well as 

 in many other examples found in the Oxford clay near Trowbridge ; 

 namely, a calcareous shelly periosteum or capsule, which invests the 

 guard, and exprnds upwards into a horny sheath or receptacle, that 

 surrounds the baal chamber of the phragmocone in which the viscera 

 were probably contained. This receptacle was formerly supposed to 

 originate from within the alveolus of the guard. Mr. Miller, many 

 years ago, inferred the existence of a vascular integument around 

 the guard from the meandring impressions of blood-vessels obser- 

 vable on the surface of some specimens ; but the presence of a cal- 

 careo-corneous capsule or sheath investing the guard, and expanding 

 into a horny receptacle, has not till now been demonstrated. 



The author considers the facts described as proving that the ce- 

 phalopod of the Belemnite was entirely distinct from the Belemno- 

 teuthis ; and that the muscular mantle, cephalic arms, and other 

 parts referred by Professor Owen to the former, exclusively belong 

 to the latter genus. 



He concludes that the remains of at least three genera of naked 



