MULTILOCULAR SHELLS. ' 245 



We now proceed to a division of shells comprising an immense 

 number of highly interesting petrifactions ; viz. 



MULTILOCULAR SHELLS. 



-This division includes three grand families, or genera, the am- 

 monites, the nautilites, and the belemnites; in all of which, the shell 

 is divided internally into numerous chambers. The body of the animal 

 has lodged in the outer chamber, but has communicated with the 

 interior chambers by a tubular substance called the siphuncle, which 

 has pierced through all the septa, or partitions. By inflating or 

 compressing this tubular substance, the animal has had the power ot 

 raising itself to the surface of the water, or sinking to the bottom. 



CoRNU AMMONis or Ammonites. Ammonite or Snakestone^ 

 We place this genus in the front of our multilocular shells, both be^ 

 cause it is the most abundant, and because it is that for which Whitby 

 lias long been celebrated. Who has not heard of the fame of our 

 petrified snakes, renowned both in fable and in song ? The shells of 

 this genus have acquired the name of snakes, from their resemblance 

 to serpents coiled up. Indeed they Avere long supposed to have been 

 real snakes; and the want of heads was no valid objection to the hy- 

 pothesis, since monkish tradition alleged, that the whole race of ser- 

 pents, by which the territory of Lady Hilda had been infested, were at 

 once decapitated and petrified, through that good saint's prayers! * 



Small shells of the helix genus, or rather of the new genus planorbiSt 

 are found recent in the river Tees, greatly resembling our ammonites 

 in their outward form, but they are not divided internally into cham- 

 bers. Notwithstanding the great number and variety of the fossil 

 anaraonites, scarcely one species has hitherto been discovered recent. 



* See History of Whitby, I. p. 313. 

 3 P 



