CARPENTER ON THE STUDY OF THE FORAMINIFERA. 
341 
nous, calcareous, and arenaceous shells; in the Perforata , with cal¬ 
careous shells only. The Imperforata never acquire double septa, 
and their supplemental skeleton, when present, is different from that 
of the Perforata. Lastly, among the Imperforata there is but one 
example (Spirillina) Gf a Monothalam with indefinite growth, and 
it is only within this division that the straight mode of growth can 
be said to attain its full development, while, on the other hand, the 
cyclical type is better manifested by Orbit olites than by Cycloclypeus. 
The distribution of the Poraminifera may be dismissed in a few 
words. The Gr omul re (which many writers would exclude from this 
order) are fresh-water as well as marine, but all the Eoraminifera 
proper exclusively inhabit the sea. Though some are litoral, the 
majority flourish best in deeper waters, and, in this respect, they 
may fairly be contrasted with the Badiolarian Bhizopods, very many 
of which assume a pelagic habit. Certain genera, more especially 
Globigerina and its immediate allies, are among the most notable 
members of the abyssal Eauna, and there is good reason to suppose 
that these may serve as food for larger animals found with them in 
the same regions. 
Glancing at their geographical distribution we are chiefly struck 
by two facts, namely—first, the wide range of several genera, as 
Miliola , Textularia and Globigerina ; secondly, the preponderance in 
tropical seas of the largest and most highly organized Eoraminifera, 
whether belonging to the perforate or imperforate series. Thus, of 
the latter, Orbiculina , Alveolina and Orbitolites; and of the former, 
Calcarina, Amphistegina and Heterostegina very imperfectly exhaust 
the list of genera restricted to the warmer seas of the globe. Cyclo¬ 
clypeus has hitherto been met with but in one locality, off the coast 
of Borneo. Other forms, of which Polystomella is a good example, 
though found in most seas, fail to attain complete development, 
whether as to size or complication of structure, outside the limits of 
the tropics. Of the forty-six genera of Eoraminifera now living, only 
twenty-seven occur in the British Eauna. Two, however, of these, 
Vertebralina and Peneroplis , would seem to be but casual inhabitants of 
cur seas, having been probably wafted thither by ocean-currents. 
Dr. Carpenter has given in an Appendix a tabular view of the revised 
“names assigned by Messrs. Parker and Bupert Jones to the species 
and varieties described and figured in Professor 'Williamson’s Mono¬ 
graph on the Becent Eoraminifera of Great Britain.” 
The general relations of the Eoraminifera to time are briefly 
summed up in the accompanying table, based chiefly on the data 
recorded by Dr. Carpenter and his coadjutors. Erom this we learn 
that, while some genera range through a number of epochs, others 
are confined to a single formation only, as Fabularia , Acicularia and 
Ovulites to the Tertiaries; Cuneolina to the Chalk; and Pusulina (the 
most remarkable of all the extinct forms of Eoraminifera), to the 
Carboniferous Limestone. 
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