162 



PROTOZOA. 



The former include a large proportion of the Foraminifei-s which 

 come under general observation, namely, the three families 

 Lagenida^ Glohigerinida and Nummulinida. They are charac- 

 terized 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 Foraminifers include the 

 families Gro7nida, Miliolida and Lituolida, in which the nature 

 of the envelope is membranous, porcellanous or arenaceous. 

 The Miliola is now the most universally diffused Foraminifer; 

 its type can be traced back to the Lias. 



Upwards of 700 fossil species of Foraminifers have been de- 

 scribed. They commence in the Palaeozoic, increase in number 

 and variety with successive strata, and attain their maximum in 

 the present seas. Indeed, they are so abundant in the most com- 

 mon materials, as chalk for example, as to justify the expression 

 of Buffon, th^t the very dust has been alive. The calcaire gros- 

 sier — the building stone of Paris, and the material of the pyra- 

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

 sea soundings show that the bed of the Ocean is composed of 

 little else than shells of Olobigerinm and the shields of Poly- 

 cystinoB. 



No. 506. Eozoon Canadense, Dawson. 





talline rocks of the Archaean of 

 Nation, Canada. 



This has been described by Principal 

 Dawson as a gigantic Foraminifer. Its 

 organic nature is still doubted, and in the 

 opinion of a large number of our best 

 authorities, is entirely disproved. The 

 fossil, if such it be, is described as con- 

 sisting of a chambered calcareous skeleton, 

 infiltrated by silicates, chiefly pyroxene, 

 serpentine and Loganite, which occupy 

 the spaces formerly filled by the sarcode 

 of the living animal. These chambers are 

 arranged in tiers, one above the other, and 

 the fossil seems thus to have formed great 

 reef-like masses, and might have originated 

 whole beds of limestone. It is the oldest 

 animal fossil known, occurring in the crys- 

 America and Europe. Laurentian, Petite 



