150 THE FOEAMINIFEEA 



segments forming a slender moniliform series. The 

 junction of one segment with the other is usually 

 marked on the stolon tube by a darker brown circlet 

 around the shell. This species is solely a recent 

 form and affects deep water. The ' Challenger ' dredg- 

 ing yields this species from samples of over 1,000 

 fathoms in every case. Goes records it from the 

 Pacific in shallower water, ranging to 300 fathoms. 

 Becent. (Plate 8, fig. C.) 



Genus A}innodi>icuti, Reuss. 



Test free, formed of a tube coiled upon itself in 

 various ways ; sometimes constricted at intervals, 

 but never septate. Garhoniferous to Becent. 



Example. — A. i i icevtuH, J)' OYhv^wy sp. {Operculina), 

 'Foram. Cuba,' 1839, p. 71, pi. vi. figs. 16, 17. 



This, the simplest form of the genus, consists of 

 a circular tube coiled in piano-spiral fashion. It 

 made its first appearance, so far as our knowledge 

 goes, in the Carboniferous limestone series, where it 

 is sometimes found in great abundance ; and it is 

 found with some frequency in nearly all later forma- 

 tions. The species is liable to great variation, the 

 tube showing various degrees of fiattening ; and it 

 often tends to depart from the plan of a fiat coiled 

 shell, and even to bend and twist on itself. The 

 structure of the test is always more or less finely 

 arenaceous. 



The specimens dredged up from existing sea 

 bottoms are often as large as 3 mm. across. A. 

 incertus has an extensive range in depth ; Goes 



