FORAMIN1FERA. 893 



discovered by Leidy amidst damp moss in the cracks of a pavement in 

 Philadelphia. In the sea the Foraminifera are universally distributed and 

 at all depths, arenaceous forms proper, i. e. Astrorhizidae, being for the 

 most part inhabitants of the deep sea, where also the Lituolidae attain 

 their highest development in size and complexity. The largest and most 

 specialised calcareous genera are found in the shallow waters of tropical and 

 sub-tropical seas. A few calcareous forms are pelagic, principally species 

 of Globigerina, Orbulina, Pulvinulina, Pullenia, and the genus Hasti- 

 gerina, all members of the family Globigerinidae. It is their tests which, 

 together with those of some non-pelagic species, in small proportions how- 

 ever, make up the Globigerina ooze, or modern chalk, which is undergoing 

 deposition at the present time over immense surfaces of the sea-bottom, at 

 depths ranging from 250 to 2900 fathoms, especially from 1000 to 2000. 

 There is reason to suppose that pelagic forms, with the exception probably 

 of Hastigerina, are capable of living also at the bottom. Foraminifera are 

 also met with in the two other deep-sea deposits, Radiolarian Ooze and 

 Red Clay. Their fauna is approximately identical according to Brady, 

 in some instances differing little from that of Globigerina ooze, though 

 naturally in relatively smaller proportion to the characteristic materials 

 of the two deposits in question. The tests of the pelagic forms however 

 which they contain are worn and corroded. In two dredgings made by 

 H.M.S. ' Challenger ' in the Pacific, both in mid-ocean, arenaceous species 

 occurred almost exclusively ; in two others minute and highly ornamented 

 Lagenae were abundant. Foraminifera are common in marine geological 

 deposits, and a large number of living genera make their appearance 

 at an early period Textularia, Lagena and Nodosaria in the Silurian, Cor- 

 nuspira, Littwla, Trochammina, Calcarina, Nummulites, &c., in the Carbon- 

 iferous, Miliolina and Globigerina in the Trias, a very large number of forms 

 in the Chalk, and especially in the Tertiary period. Alveolina, Operculina 

 and Nummulites are genera which, though living at the present day, were 

 particularly numerous in Eocene times ; and the last-named especially con- 

 tributes largely to the building up of limestones of that age in Central 

 Europe, Central and Southern Asia, and Northern Africa. Many arena- 

 ceous genera (Astrorhizidae and Lituolidae], still living in the deep sea, 

 are found in the Lias and attain their maximum development before the 

 Cretaceous period. Of extinct forms, one Eosoon, of doubtful animal 

 nature however, is found in Pre-Cambrian strata. It is supposed to have 

 consisted of tiers of more or less oval chambers with perforated walls, 

 connected by vertical canals and an intervening supplemental skeleton 

 with interseptal canals ; the chambers in each tier have usually wide open- 

 ings into one another ; the whole structure covered surfaces a foot square 

 with masses 5-6 in. thick. Among Lituolidae the Endothyrinae extend 

 from the Carboniferous into the lower Oolite ; Parkeria is confined to 



