i 30. BELEMXITES OF THE CHALK. 337 



there are none that have excited so much curiosity, and given 

 rise to so many conjectures as to their nature and origin. 

 as the fossils termed Bele /unites by geologists, and which 

 are generally known as thunderbolts. These are long, 

 cylindrical, or fusiform stones, more or less pointed at one 

 extremity, and having at the other and larger end a conical 

 cavity, which is either occupied by a chambered shell, or 

 filled up with the clay, sand, or stone, in which the be- 

 lemnite happens to be imbedded. The substance of these 

 bodies is invariably calcareous spar, of a radiated structure 

 (Lign. 66, Jig. 1). Such are the usual characters of these 

 fossils, of which there are numerous species ; certain forms 

 abounding in the cretaceous strata. A very common chalk 

 belemnite is figured Lign. 66. jig. 1 ; and a peculiarly 

 transparent species from the Gait, Lign. 63, Jig. 5. These 

 bodies were the osselets of cephalopods allied to the Sepia, 

 which possessed an ink-bag, mandibles, large eyes, and arms 

 furnished with acetabula or suckers, and slender, elongated, 

 hooks.* 



30. Crustaceans of the chalk. f — Specimens of 

 several genera of crustaceans have been obtained from the 

 Sussex chalk ; among these are three or four species of 

 Astaeus or Lobster, in which the filiform antennae, the 

 abdominal segments, and the caudal appendage, or tail, are 

 preserved/ 



In the Gait, the crustaceans hitherto discovered belong- 

 to very small species. I have obtained from Kingmer, 

 near Lewes, and Folkstone, specimens of several extinct 

 forms, which are related to Indian genera. § In the 

 Speeton clay of Yorkshire, Professor Phillips has dis- 

 covered a beautiful species of Crayfish. |j The green - 

 sand of Kent, Dorsetshire, and the Isle of Wight, has 



* Medals of Creation, vol. ii. p. 469. f Ibid. p. 53d. 



J Ibid. p. 537. § Ibid. p. 532. ii Ibid. p. 540. 



