186 PKOTOZOA. 



dial segment, sometimes in a straight line, more commonly in a spiral or 

 discoidal form. It is usually a sedentary organism, being fixed by the 

 adhesion of the shell to the surface of Algae, Zoophytes. Molluscs, etc. 

 D'Orbigny's classification, founded on the numerical increase of tho 

 chambers, has been set aside. Carpenter divides the Order into two 

 primary groups according as the envelope is per/orated or imperforated. 

 The former include a large proportion of the Foraminifers which come 

 under general observation, namely, the three families, Lagenida, Glo- 

 bigerinida, and Nummulinida. They are characterized by a calcareous 

 shell perforated by tubular openings. The extraordinary multiplication 

 of Nummulites in the Eocene gives the last family a place of no mean 

 importance as a member of its fossil fauna. The imperforated Foramini- 

 fers include the families, Gromida, Miliolida, and Lituolida, in which 

 the nature of the envelope is membranous, porcellanous and arena- 

 ceous. The Miliola is now the most universally diffused Foraininifer ; 

 its typ e can be traced back to tbe Lias. 



Upwards of 657 fossil species of Foraminifera, belonging to 73 

 genera, have been described. They commence in the Palaeozoic age, 

 increase in number and variety with each successive stratum, and attain 

 their maximum in the present seas. Indeed, they are so abundant in 

 the most common materials, as chalk for example, as to justify the ex- 

 pression of Buffon, that the very dust had been alive. The calcaire 

 grossier — the building stone of Paris, and the material of the Pyramids, 

 are full of these minute chambered shells ; while the deep-sea soundings 

 of the Atlantic Telegraph Company show that the bed of the Ocean is 

 composed of little else than the shells of Globigerinse and the shields of 

 Polycystinse. 



1. Sub-Order, Foraminifera perforata. 



Nummulinida. 

 No. 964. Amphistegina Lessonii D'Orb. 



Living : Isle of France. 



No. 965. Amphistegina Quoyi, D'Orb. 



Living : Isle of Rawak, Pacific. 



No. 966. Amphistegina vulgaris, D'Orb. 



Miocene : Bordeaixx, France. 



