18 



Dr. Mantell on the Structure of the Belemnite. 



'ig. 



very thick and heavy, and invariably mineralized by calc spar : 

 the original structure was probably light and calcareous, like 

 that of the osselet of the Sepia, 



3. The Capsule^ or sheath; a thin horny or testaceous case 

 which invested the osselet, and constituted the external envelope 

 of the receptacle ; it is seen partially covering the osselet at c, 

 fig. 1, and in section at e, /, fig. 2. This structure was for the 

 first time demonstrated in my memoir, 'Phil. Trans/ 1848. 



With the exception of obscure indications of a carbonaceous 

 fibrous structure between the dorsal processes, the above descrip- 

 tion comprehends all the facts re- Yig:. 3. 

 lating to the organization of the 

 Belemnite with which we are at 

 present acquainted : no soft parts, 

 no traces of arms or tentacles, 

 no vestiges- of the eyes or man- 

 dibles, have been discovered. 



The Belemnoteuthis. — From 

 the extraordinarily perfect state in 

 which some examples of the Be- 

 lemnoteuthis are met with, a brief 

 description will suffice. Fig. 3 

 (from a drawing with which Mr. 

 Woodward of the British Museum 

 has favoured me) exemplifies the 

 essential parts of the structure of 

 these Cephalopods. The body is 

 of an elongated form, with a pair 

 of lateral fins, two large sessile 

 eyes, eight uncinated arms, and a 

 pair of armed tentacles ; each arm 

 was furnished with from twenty to 

 forty pairs of hooks, placed alter- 

 nately (fig. 4, 4). Like the Sepia 

 it had a pigmental sac or ink-bag, 

 which is generally filled with the 

 inspissated secretion. The inferior 

 part of the body is of a conical 

 form, and contains a brown horny 

 osselet, with a siphunculated phrag- 

 mocone, which terminates in a 

 rostrum of a fibrous structure 

 (fig. 4, 5). The osselet of the 



a, the uncinated arms and tentacles ; b, remains of the head and eyes ; c, 

 the mantle, with indications of fins ; d, the pigmental sac or ink-bag ; 

 e, the osselet : the transverse lines indicate the septa of the phragmo- 

 cone, which is covered by a horny sheath or capsule ; /, the solid termi- 

 nal apex of the osselet. 



Belemnoteuthis antiquus 

 (4 natural size, linear). 



