ANIMALCULITES OF THE CHALK. 



321 



There is a fossil zoophyte (Choanites K'dnigi) which is 

 well known to collectors of Sussex pebbles bj the name of 

 petrified sea-anemone, from its supposed resemblance to 

 the living Actinia (P/. VI. fig. 11); but the original was 

 a very different creature. From an extensive suite of spe- 

 cimens, I have ascertained that it was of a pyriform shape, 

 with a central opening, from which numerous tubes radi- 

 ated ; and these are oftentimes exquisitely preserved in 

 flint. The external surface frequently exhibits the remains 

 of crucial spines, similar to those possessed by the recent 

 alcyonia.* 



Certain polypiferous zoophytes {Ventriculites) are exceed- 

 ingly numerous in the chalk near Lewes and Brighton ; 

 and being often preserved partly in chalk and partly in 

 flint, give rise to most interesting specimens, which throw 

 light on the segregation of silex from the thermal streams 

 holding that mineral in solution, which were periodically 

 erupted into the calcareous sediments of the chalk ocean, f 



17. Animalculites of the chalk. — Under this head 

 I will notice some of the minute organisms of the cretaceous 

 system. The term animalculites, though not strictly appli- 

 cable to all the microscopic fossil Infusoria, may be con- 

 veniently employed to designate the remains of animalcules 

 of the most simple structure; and poly thalamia, to denote 

 the chambered shells of the foraminifera ; as rotalia (p. 249), 

 textilaria, &c.J 



The Foraminifera are marine animals, of low orga- 

 nization, and, with but few exceptions, extremely minute ; 

 in an ounce of sea-sand between three and four millions 



* Thoughts on a Pebble, pi. 1 & 2. Medals of Creation, vol. i. 

 p. 264. 



f See Medals of Creation, vol. i. p. 274. 



% Want of space compels me to refer the reader for many details on 

 this subject, to my " Notes on a Microscopical Examination of Chalk 

 and Flint," in the Annals of Nat. Hist. 1845. 



T 



