﻿W. J. Sollas—The Getius Wehhina. 103 



like it, to a piece of coprolite, which in this case, however, had 

 become imbedded togetlier with other foreign material in the second- 

 ary deposit of 'coprolite' which had finally tilled 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 examples 

 of the supposed Wehhina 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 Ventriculite is that of one of the Cambridge 

 Greensand Wehhincs, and thus available for further observations; and 

 next, and most important, that these Webhince are truly perforate 

 foraminifera. 



On returning now to a closer examination of the external cha- 

 • racters of these forms, one finds that they comprise two kinds, one 

 ornamented with irregularly dispersed, more or less conical tubercles, 

 the other with a perfectly smooth plain surface ; the latter I pro- 

 pose to call Wehhina IcBvis, and the former W. tubercidata. 



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 forms 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 Wehhina. 



Genus Webbina. (PI. VI.) 



General Characters. — Consisting of a single more or less hemi- 

 spherical, ovoidal, or pyriform chamber, terminated in many cases 

 by a short narrow open tubular 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 test, 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 

 shown in section as the fine line "I" 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 canaliculi, less than 0-00006 of an 

 inch in diameter. These are well shown in Fig. 7, and on a larger 

 scale ( X 540) in Fig. 8. 



Species. — 1. W. loBvis, mihi, Figs. 1, 2, 3. Surface of test smooth, 



