372 MANUAL OF NATURAL HISTORY. 



FORAMINIFERS. 



These singular animals until recently were regard- 

 ed as a distinct order of Cephalopodous Mollusks, 

 which the polythalainous nature, and general ap- 

 pearance of their small shell-like skeletons, seemed 

 to authorize, Although the organization of the 

 vital portion of their bodies appears so simple, yet 

 these little nautiloid shells are remarkable not only 

 for their beauty and varied forms, but for a certain 

 degree of complexity in their structure. Minute as 

 are the Foraminifera, they yet are powerful auxi- 

 liaries to the coral-forming Polypifera, in building 

 up islands in the middle of the ocean, in obstructing 

 navigable channels, and in gradually filling up bays 

 and harbours. They are found in the greatest 

 abundance on the sandy shores of tropical coun- 

 tries, although very numerous forms are met with 

 on our own coasts. Nine hundred species belong- 

 ing to sixty-eight genera, have been described by 

 D'Orbigny, from existing seas, and it would appear 

 that in the fossil state they are no less numerous, 

 the same eminent naturalist having discovered and 

 recorded thirty genera, consisting of two hundred 

 and fifty species in the Cretaceous formation only. 

 In order to render their forms obvious to the eye 

 of the casual observer, M. D'Orbigny made exquisite 

 models on a large scale of the different genera, 

 copies of many of which, in plaster of Paris, may 

 be observed in the British Museum. 



