LITUOLIDA. 25 
Famity—LITUOLIDA, Carpenter. 
Genus—TrocHaMMiINnA, Parker and Jones. 
Wespina, D’ Orb. (in part). 
Rotauina, Williamson (in part). 
TrocuaMMINA, Parker and Jones, Reuss, Carpenter, and Brady. 
Ammopiscus, Reuss (?). 
General characters.—Shell free or attached, very variable in form, consisting of one 
or many chambers. ‘Texture arenaceous, the sandy constituents being held together by 
an ochreous cement, and not projecting above the surface, which is smooth.  Poly- 
thalamous varieties have no proper septa; but the division into chambers is effected by 
constriction or infolding of the primary shell-wall. 
The genus Zrochammina differs from Zituola and the other arenaceous genera in the 
fact that, although its walls are chiefly built up of sand-grains, the particles are so 
incorporated in the calcareous cement that the surface of the shell is usually quite smooth. 
The solitary specimen, on the strength of which we accept Zrochammina (Webbina) 
irregularis as a Crag species, is perhaps the most obscure form of the genus, and one 
which may be readily overlooked. It consists of a minute, subconical, tent-like, circular 
disc, growing parasitically on a flat bit of shell, and presenting no character to arrest the 
attention. Indeed, it is only by the knowledge gained in the examination of a large 
number of specimens that we are enabled to recognise its affinities, or even to satisfy our- 
selves of its belonging to the Foraminifera. 
The simplest forms of Zrochammina belong to a species (Z. [Webbina] irregularis, 
D’Orb.) of which we have four varieties ; and, since it is useful to have a “ subgeneric” 
name distinguishing them from Zrochammina proper (as is the case with so many other 
Foraminiferal groups), we have proposed (‘ Phil. Trans.,? 1865, p. 435) to retain 
D’Orbigny’s term “ Webdina,” applied by him to one of them, although first used for a 
few-chambered, uniserial, curved form of Nudecularia rugosa (‘ Foram. Canaries,’ p. 126, 
pl. 1, figs. 16—18 ; and ‘ For. Foss. Vien.,’ p. 74, pl. 21, figs. 11, 12). 
1. Webbina irregularis, D’Orb., is adherent, moniliform, with more or less oval 
chambers, and varies in the relative length of its stoloniferous connecting tubes, in the 
number of its chambers, and in the straightness or curvature of their line of growth. 
Sometimes the stolons bifurcate, giving rise to a branching arrangement of a few cham- 
bers, common in strata of Cretaceous age, the Oxford Clay, &c. (‘ Quart. Journ. Geol. 
Soc.,’ 1860, vol. xvi, p. 304; ‘Carpenter’s Introd. Foram.,’ 1862, p. 141, ph ll, 
figs. 8, 9). 
2. Webbina irregularis alternans, P. & J., is adherent, and has the stolons issuing 
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