60 Trochammine of the Lower Malm of Aargau. 
With the exception of small serpuloid bodies attached to a 
valve of Lima from the Muschelkalk of the Rhine valley, 
which are possibly remains of Webbine, no traces of Fora- 
minifera have been detected in the Trias of the Canton Aar- 
gan. Inthe Sinemurian limestones with Amm. Bucklandi and 
Gryphea arcuata, numerous genera (Lagena, Nodosaria, Den- 
talina, Vaginulina, Marginulina, Cristellaria, Frondicularia) 
are represented by many, Cornuspira, Textilaria, Placopsilina, 
and a small Trochammina or Endothyra by one very rare 
species. 
Throughout the whole Lias this fauna remains almost un- 
changed, except that Tewtilaria and Cornuspira disappear 
towards the upper strata. 
With the Dogger, Trochammina, Valvulina, Endothyra, 
Plecanium, and Spirillina appear. Miliola reaches its greatest 
development in the Jurassic formation, and several other 
genera, as Lituola, Textilaria, and some types of Nodosaria, 
become more abundant than in the Lias. 
At the end of the Callovian period a great change in the 
general lithological and paleeontological character of the sedi- 
ments takes place, which is particularly remarkable from the 
sudden appearance of a rich fauna of siliceous sponges. 
Here the Foraminifera with sandy or partly sandy shells 
form the greater part of the microscopic fauna. Only a few 
of the Liassic types of Lagena, Nodosaria, Dentalina, &e. 
are still traceable. The Textilarians are the most conspicuous 
through the great number of closely-allied varieties of the 
Sagittula group. ‘Towards the younger zones several genera 
(Frondicularia, Globigerina, &c.) disappear, and others (No- 
dosarta, Dentalina, Vaginulina, Marginulina) become gra- 
dually scarcer; but the imperfect knowledge of the upper 
Sequanian and the Kimmeridgian sediments does not allow 
of giving a satisfactory list of the Upper Jurassic Rhizopods. 
It is interesting to observe several widely distinct macro- 
scopical faunas in the Malm, differently developed according 
to considerable changes in the nature of the sea-bottom; whilst 
the Foraminifera seem to have adapted themselves much 
more easily to the new conditions of life, thus giving birth to 
many interesting varieties, which, without numerous inter- 
mediate forms, it would be absolutely impossible to recognize 
as mere descendants of the typically-formed species of the 
Lower Malm. 
The greatest impediment to Swiss geologists arises from 
the want of many of the most important works on Foramini- 
fera, which makes a careful study of the many important 
microscopical species almost impossible, and which accounts 
