but the upper chamber is equally proportionable to the bulk, or circum- 

 ference of the belemnite, of whatsoever size or shape, and is the seat OF 

 dwelling place of the animal that forms the belemnite.' 



Whoever (Mr. Platt says) considers the seam or sulcus in the belem- 

 nite, will, I think, conclude with me, that the outward lamina is 

 formed latest, as in the cowree, and that the seam or sulcus is caused 



by the several additional coverings or laminae terminating there. 



As the oyster strengthens its shell,, and excludes its first habitation, by 

 additional laminae formed within, the belemnite incloses its dwelling, by 

 adding new laminae without. Mr. Platt supposes, that the animal growing 

 larger, when in its first formed cell, forms then a second cell or cham- 

 ber, and at the same time covers the first cell, by forming the appen- 

 dage or guard, which is the first stage of the belemnite. In forming the 

 third cell, fresh laminae or coverings are carried on, and so of the 

 rest, the body of the belemnite gaining an increase of volume with each 

 additional chamber. 



The siphunculus of the belemnite, he observes, is always upon the 

 verge of the chamber or cell ; and, in this siphunculus, is a little gut or 

 ductus, proceeding from the body of the animal, by dilating or contract- 

 ing of which, the animal, it should seem, may go out or in to its cell at 

 pleasure. This is the only stay which the animal has to secure its 

 retreat. But I cannot agree (he says) with the learned Dr. Hooke, 

 " that the gut, or ductus, passes through all the cells to the end of the 



spiral cone, either in this shell or the nautilus. 1 am apt to think, 



(Mr. Platt says) that this gut, or ductus, as well as the body of the 

 creature, is capable of being extended very considerably, to serve all 

 the uses of forming the belemnite, without leaving the siphunculus ; and 

 that the gut serves for the same purposes as the tendons of the oyster i 

 the latter to open and shut the shell, the former to allow the animal to 

 go out and in at pleasure. And as the oyster feeds altogether m the 

 shell, by opening the verge, the belemnite (whose residence is in the 

 great deep,, which is seldom disturbed) very likely goes out in quest of 



