628 
THE VOYAGE OF H.M.S. CHALLENGER. 
Rotaliform or lenticular varieties being placed at or near tbe peripheral margin. The 
PulvinulincB are always finely porous and the test (with only two or three exceptional 
species) is almost invariably regularly Rotaline ; the sutures are often limbate externally, 
but the surface hardly ever otherwise ornamented. The genus Rotalia attains a somewhat 
higher type of structure than its allies, the well-characterised forms having double septa 
and an interseptal skeleton, the latter often traversed by a more or less complex system 
of canals ; whilst the smaller varieties, which have no supplemental skeleton, betray their 
relationship by the thickened and granulose edges of the sutures on the inferior side. 
The connection of Rupertia and Carpenteria with the foregoing genera, through the 
subconical Planorbulince, is easily traced. The former in its early stage has a Truncatu- 
lina- like shell, which grows adherent by its superior face ; and the subsequent whorls, 
which are of nearly uniform diameter, are superimposed vertically instead of peripherally, 
so as to form a columnar test, the aperture of which is at the inner margin of the terminal 
segment. The relationship of Carpenteria is best understood from Carpentaria monti- 
cularis. In the young condition the test, which is scarcely distinguishable from that of 
Truncatulina refulgens, consists of a depressed cone growing attached by its superior 
lateral surface ; the aperture, however, at a very early stage becomes apical or nearly so, 
and the later chambers assume an elongated and irregular contour, spreading radially. 
Some species of Carpenteria exhibit double septal walls and a rudimentary canal system ; 
but this is not a constant or even a usual feature. 
Calcarina differs from Rotalia chiefly in the excessive development of the supple- 
mental skeleton, which not on]y fills the umbilical cavity of the test, but forms the 
peripheral spines that characterise the genus. 
The Sub-family Tinoporiile embraces a number of types, the Rotaline affinity of which 
is not quite so apparent. The test of Tinoporus consists of a central piano-spiral disk, 
with chamberlets piled on either side in more or less regular tiers ; and it is furnished 
with a supplemental skeleton, which manifests itself externally in radial spines like those 
of Calcarina. The closely allied Gypsina has likewise a spiral nucleus, though of minute 
dimensions, with chamberlets clustered around it either in one plane or more or less 
equally on all sides. Neither of these types present any general aperture, external com- 
munication being maintained by the coarse perforations of the chamber- walls. Aphrosina, 
on the other hand, has a similar test, of irregular convex shape and spreading habit, with 
numerous marginal orifices. 
The somewhat aberrant genus Polytrema displays intermediate characters. Its 
affinity to the Tinoporinae is indicated by its numerous minute chambers disposed 
in more or less regular layers, and by the absence, in the encrusting varieties, of any 
general aperture ; whilst the monticular apertural processes of the arborescent forms 
suggest their near relationship to Carpenteria. 
By some recent authors the genus Cymbalopora has been placed amongst the Globi- 
