356 Dr. R. Hausler on the Trochamminz 
possible to extract their perfect tests from the hard materials. 
One thin layer, without any traces of larger fossils, is excep- 
tionally rich in T. incerta, so that on one occasion a single 
drop of the washing contained twenty-five specimens. In 
this bank the minute tests of a curious new variety are not 
uncommon :— 
Trochammina incerta, var. granulosa, nov. (Pl. XV. fig. 1.) 
Test free, discoidal, small, regularly convoluted in one 
plane. Convolutions numerous, partly embracing, of nearly 
uniform diameter ; oldest convolutions covered with variously 
distributed minute tubercles ; last convolution smooth. Aper- 
ture simple, at the non-constricted end of the chamber. 
Test fine, arenaceous, transparent; cement calcareous, 
colourless. Surface smooth, rarely rough. Diam. 0-1 
millim. 
This little transparent variety is sometimes difficult to dis- 
tinguish from a Spirillina when viewed with a low power, as 
the small tubercles, when arranged regularly in radial or spiral 
rows, give the shell the appearance of a perforated species. 
T. (Amm.) incerta, var. granulosa, resembles some liassic 
varieties of Involutina*, sometimes also Spirillina mar- 
garitifera | ; but the shell is never biconvex as in the former, 
so that generally all the convolutions are visible. 
Trochammina incerta, var. gracilis, (Pl. XV. fig. 3.) 
Cornuspira gracilis and C. media, Kubler & Zwingli, /. c. p. 17, pl. ii. 
fig. 4, p. 38, pl. iv. fig. 2. 
Test free, discoidal, regularly convoluted in one plane, 
composed of a non-septate rounded tube of almost invariable 
diameter. Convolutions numerous, eight to twelve; aperture 
simple. . 
Test fine, arenaceous; cement calcareous, hyaline. Surface 
almost smooth. Diam. 0:1 millim. 
Trochammina incerta, var. megasptra, nov. 
(Pl. XV. fig. 4.) 
Test free, discoidal, regularly convoluted, composed of a 
non-septate, generally angular tube of nearly uniform width, 
constricted at irregular intervals. Convolutions numerous, 
eight to twelve, in one plane. 
Test thin, very finely arenaceous; cement calcareous, brown- 
ish. Surface smooth. Diam. 0:1 millim. 
* Mém. Acad. Imp. Metz, 1860-61, pl. vi. fig. 22; Zeitschr. deutsch. 
geol, Ges. 1874, pl. xviii. fig. 3. 
+ Williamson, Rec. For, Gt. Brit. pl. vii. fig. 204. 
