REPORT ON THE FORAMINIFERA. 
629 
GEBXNTXyE, and a good deal might be said in favour of this view ; but on the whole it^most 
natural position appears to be in the Rotaline series, in the immediate vicinity either of 
Pcitellina or of Planorbulina. Again, the genus Rotalia has been removed by Moebius 
from the other Rotaline genera, and classed with Operculina, Ileterostegina, and their 
allies, on account of the complicated canal system with which the more highly developed 
species are endowed. It must, however, be borne in mind that it is only a portion of the 
genus that is so characterised ; that the structure of some of the smaller species is as 
simple as the feeblest Discorbince, and that of the majority only so far advanced as to 
have double septal-walls ; whilst, on the other hand, certain allied genera, such as Tinoporus 
and Carpenteria, exhibit to a greater or less degree the same tendency to produce an 
interseptal skeleton with its almost invariable accompaniment of ramifying canals. The 
presence or absence of a canal system, though important from a structural point of view, 
is not a character upon which a primary distinction of this sort can be founded. 
Sub-family I. Spirillininse. 
Spirillina, Ehrenberg. 
Spirillina, Ehrenberg [1841], Parker and Jones, Williamson, Carpenter, Giimbel, Brady, Kiibler 
and Zwingli, Terquem, Siddall, Bertkelin, Moebius. 
Ojperculina, pars, Reuss [1849]. 
Cornuspira, pars, Scknltze [1854]. 
Oyclolina, Egger [1857]. 
The essential characters of the genus Spirillina may be summed up in few words. 
The test consists typically of a non-septate tube coiled symmetrically on itself on one 
plane ; the walls are hyaline and perforate, and the open end of the tube serves as the 
aperture. The deviations from the normal plan of growth are few and insignificant, and 
seldom amount to more than a certain degree of asymmetry in the form and disposition 
of the coils. The shell is typically free, in rare instances parasitic. The minor charac- 
ters on which the specific or varietal subdivision of the genus is founded are derived 
mainly from the sectional contour of the tube and the condition of the exterior of the 
test, with respect to surface-ornament, sutural limbation, and the like. 
The genus Spirillina is isomorphous with Cornuspira and Ammodiscus, the three 
types occupying analogous positions in the calcareous and perforate, the calcareous and 
imperforate, and the arenaceous groups of Foraminifera. 
The Spirillince are for the most part of minute dimensions. They find a home in 
every part of the world, preferring comparatively shallow^, muddy sea-bottoms. They 
are seldom met with in the fossil state ; nor, as far as at present known, do they occur in 
older formations than those of the Miocene period. 
(ZOOL. CHALL. EXP. PART XXII. — 1884.) 
Y 80 
