REPOET OH THE FORAMINIFERA. 
369 
ture, normally a transverse fissure, sometimes takes the form of a bordered lateral orifice, a 
rounded central perforation, or a number of pores on the distal face of the last segment ; 
so in Bigenerina, though represented typically by a central rounded opening, it frequently 
assumes the character of an oval, elongate, or fissurine orifice, or of a number of terminal 
pores. 
Many of these characters will be referred to again in the description of the species by 
which they are exemplified. The importance of some of them has been exaggerated, and 
in certain cases they have been treated as distinctions of generic value ; but amongst the 
typical Textularice in which their relative significance is more easily observed, such 
peculiarities are found in many instances insufficient for even specific diagnosis, and there 
can therefore be no good reason for making them a basis for the generic subdivision 
of a comparatively small subordinate group like the Bigenerince. 
The geographical distribution of the genus Bigenerinci presents somewhat marked 
features. It is very common in the North Atlantic, tolerably common in the Mediter- 
ranean and Adriatic, and much less frequent in the South Atlantic, whilst it is very rare in 
the North Pacific, and almost entirely wanting in the Southern Ocean and the South Pacific. 
In the fossil condition it is met with in various Tertiary formations, making its first 
appearance in the Eocene period. 
Bigenerinci nodosaria, d’Orbigny (PI. XLIY. figs. 14-18). 
Bigenerina nodosaria , d’Orbigny, 1826, Ann. Sci Hat., vol. vii. p. 261, Ho. 1, pi. xi. figs. 9-12. 
— Modele Ho. 57. 
,, pusilla, Roemer, 1838, Heues Jahrb. fur Min. &c., p. 384, pi. iii. fig. 20. 
„ agglutinans, d’Orbigny, 1846, For. Foss. Vien., p. 238, pi. xiv. figs. 8-10. 
,, turulosa, Costa, 1856, Atti dell’ Accad. Pont., vol. vii. p. 285, pi. xv. fig. 12. 
„ anulata, Id. Ibid. p. 284, pi. xv. fig. 13. 
,, bifida , Id. Ibid. p. 287, pi. xxiii. fig. 1. 
Clavulina elegans, Karrer, 1864, Hovara-Exped., geol. Tbeil, vol. i. p. 80, pi. xvi. fig. 11. 
Textularia agglutinans, var. ( Bigenerina ) nodosaria, Parker and Jones, 1865, Phil. Trans., vol. civ 
p. 371, pi. xv. fig. 25 ; pi. xvii. fig. 80. 
Bigenerina nodosaria, Terrigi, 1880, Atti dell’ Accad. Pontif., ann. xxxiii. p. 192, pi. ii. fig. 28. 
In Bigenerina nodosaria the Textularian portion of the test is much compressed, and 
tapers to a point at the aboral extremity. It is generally also a good deal broader than 
the adjoining segments of the linear series, and the alternate arrangement of the chambers 
is more or less distinctly marked externally. The uniserial portion in adult specimens 
consists of about four segments, each somewhat larger than its predecessor, usually gibbous 
or rounded in contour, and the sutures correspondingly sunken. 
Bigenerina nodosaria is a common North Atlantic species. It has been met with as 
far north as the Hunde Islands, Davis Strait, 25 to 70 fathoms (Parker and Jones) ; and 
occurs in the Faroe Channel, 155 fathoms ; off Shetland and amongst the Hebrides, 80 to 
