28 DR. It. HAFSLER ON SOME UPPER 



Thframmina hemispheric a, Hausl. Plate III. figs. 7-9. 



Test invariably fixed, nearly hemispherical, monothalamous, 

 with few indistinct papillae placed round the margin. 



Test finely arenaceous, very thin, transparent. Diam. 0*5 mm. By 

 its simple, more or less hemispherical chamber, the smallness and 

 arrangement of the few papillae, and the very thin, hyaline test this 

 species is easily distinguished from the fixed varieties of Th. 

 'papillata. 



T. hemisphcerica is not common, but widely distributud in the 

 zones of Amm. transversarius and A. bimammatus. 



From these few notes we may conclude that probably most of the 

 recent genera of Astrorhizidae and Lituolidae were already represented 

 in Mesozoic sediments, either by the same or nearly allied species. 



Though the zone of Amm. transversarius and chiefly its sponge- 

 beds are the richest in arenaceous Foraminifera amongst the Upper 

 Jurassic sediments, yet a careful study of the microscopic remains of 

 the younger beds is sure to yield better results in time. Amongst 

 these the zone of Amm. bimammatus (etage Sequanien I.) with a 

 well-developed fauna of hexactinellid sponges is undoubtedly the 

 richest ; but the collecting offers great difficulties. A good many 

 Astrorhizidae and Lituolidae were, however, collected about six years 

 ago at Auenstein, Eemigen, and the Khyfluh. 



From the zone of Amm. tenuilobatus about ten species are known 

 from Baden and the Lagern. The English Upper Jurassic deposits 

 seem to be much less rich in arenaceous Foraminifera. 



The distribution within the limts of the zone of Amm. transver- 

 sarius is very irregular, so that up to the present time certain spe- 

 cies are known only from a small district or even a single locality, 

 where the conditions for their preservation must have been specially 

 favourable. 



With the typical forms we meet in almost every zone with varie- 

 ties or monstrosities from which many interesting facts concerning 

 the relationship of widely different species may be obtained. 



As a rule, we observe amongst the Jurassic Astrorhizidae and Litu- 

 olidae that all the hosts of varieties show a strongly marked tendency 

 to fall back into the simplest typical forms, which, from their wide 

 geological range, we are obliged to suppose possess the greatest 

 chance of surviving in the struggle for existence. 



EXPLANATION OF THE PLATES. 



Plate II. 



Fig. 1. Psammosphcera fusca, Schultze. 



2-6. Hyperammina vagans, Brady (spiral var.). 

 7. Eeophax seorpiurus, Montf. (?). 

 8-10. Eeophax helvetica, Hausl. 



Plate III. 



Fig. 1. Placopsilina cenomana, d'Orb. 

 2-5. Thurammina papillata, Brady. 

 6. Thurammina papillata upon Hyperammina vagans. 

 7-9. Thurammina hemispheric a, sp. nor. 



