W. J. So/las — The Genus Webbina. 
103 
like it, to a piece of coprolite, which in this case, however, had 
become imbedded together with other foreign material in the second- 
ary deposit of ‘coprolite’ which had finally lilled up the cloaca of the 
sponge. Both these sections exhibited in an unmistakable manner 
the tubulation of the shell-wall which distinguishes the Vitrea per- 
forata. This observation led me to select some characteristic exaraples 
of the supposed Webbina irregularis for the purpose of grinding them 
down into thin slices ; and on examining the sections which had been 
thus prepared, the same tubulated structure was clearly revealed. 
Thus then two things were proved : first, that the section which had 
been first observed in the Yentriculite is that of one of the Cambridge 
Greensand Webbince, and thus available for further observations; and 
next, and most important, that these Webbince are truly perforate 
foraminifera. 
On returning now to a closer examination of the external cha- 
racters of these forins, one finds that they comprise two kinds, one 
omamented with irregularly dispersed, more or less conical tubercles, 
the other with a perfectly smooth plain surface ; the latter I pro- 
pose to call Webbina Icevis, and the former W. tuberculata. 
The only difference which I can distinguish between W. Icevis 
and Trochammina irregularis exists in the structure of their shell- 
walls ; vitreous and perforate in the one, imperforate and arenaceous 
in the other. Since, however, this distinction (according to the 
generally received Classification) is a fundamental one, it requires 
some recognition in our nomenclature, and I venture to suggest that 
those Webbina-like forins which are distinctly arenaceous should 
not receive any other generic designation than that of Trochammina ; 
while those which are perforate should possess the exclusive right to 
D’Orbigny’s name of Webbina. 
Genus Webbina. (PI. YI.) 
General Ckaracters . — Consisting of a single more or less liemi- 
spherical, ovoidal, or pyrifonn chamber, terminated in many cases 
by a short narrow open tubulär Prolongation, or a succession of such 
chambers in variable number, connected together in a moniliform 
series, varying in direction of growth, and increasing in size from 
the first formed onwards ; always adherent to some foreign body, the 
surface of adherence furnishing the immediate boundary wall to one 
side of the cavity of the fest, except near the circumference of the 
chamber, where the foreign substance is overgrown by an im- 
measurably thin structureless calcareous film or lamina, which is 
sliown in section as the fine liue “Z” in Fig. 7. White and opaque, 
tending especially in W. Icevis to become colourless and translucent ; 
surface smooth or tuberculate ; size variable, the smallest chamber 
observed measuring 0-005, and the largest 0-03 of an inch in length. 
Minute Structure. — The test is traversed throughout, in a direction 
normal to its surface, by very fine caualiculi, less than 0-00006 of au 
inch in diameter. These are well shown in Fig. 7, and on a larger 
scale ( x 540) in Fig. 8. 
Species. — 1. W. Icevis, mihi, Figs. 1, 2, 3. Surface of test smooth, 
