Trochammine of the Lower Malm of Aargau. 349 
XXXV.—Additional Notes on the Trochammine of the Lower 
Malm of the Canton Aargau, including Webbina and Hor- 
mosina. By Dr. Rupotr HAuster, ¥.G.S8. &e. 
[Plate XV.] 
In my last paper on the Trochammine of the Lower Malm of 
the Canton Aargau (Switzerland) reference was made to some 
polythalamous species as probably belonging to T. squamata, 
T. inflata, T. coronata, T. vesiculata, and T. Reussi. 
All the regularly septate rotaline Foraminifera, which in 
a previous memoir I described as Rotalidee with their shells 
entirely changed by pseudomorphoses analogous to those which 
altered the chemical nature of other organic remains of this 
zone, have been found to be true Trochammine, since more 
abundant material has been obtained from the Upper Batho- 
nian stage and almost all the various zones of the Argovian 
Malm. 
In accordance with Brady’s views on the relationship of 
some fixed and other free Nodosaria-like forms to the typical 
Trochammine, we unite a small number of interesting forms 
of Webbina and Hormosina with the genus Trochammina in its 
widest sense. However dissimilar the external appearance of 
these new Jurassic fossils may be when compared with the ro- 
taline Trochamminc, yet the microscopical texture of their 
shells gives sufficient reason for placing them in the immediate 
neighbourhood of the unilocular varieties of Ammodiscus. 
We are at present not prepared to give an exhaustive 
treatise on all the numerous varieties, from want of sufficient 
material ; but the most characteristic forms shall be briefly 
described, in order to add further proofs of the wide geological 
range of certain species which have hitherto been but little if 
at all known from the Upper Jurassic formation. 
As a rule their tests are minute, thin, and very fragile ; 
for this reason their examination presents great difficulty, 
especially when they are imbedded in hard marly material, 
from which perfect specimens are extremely difficult to extract. 
The forms allied to Hormosina were described (J. ¢.) as 
silicified Nodosarice and Dentaline ; but there can be no doubt 
as to their true position among the arenaceous Foraminifera. 
The fixed Trochammine (Webbine) are very feebly deve- 
loped in the whole Jurassic series; and only two distinct species 
have been found in the zone of Ammonites transversarius. 
Amongst the rotaline Trochammine all the species except 
T. constricta are very variable, and furnish us with new series 
