

264 Dr. Rudolf Hausler on Jurassic Varieties 



and localities, we find that the species can be divided into a 

 number of groups, each of which contains some characteristic, 

 and often remarkably constant, varieties. But, owing to their 

 great variability, most of them can be connected through 

 intermediate forms, forming thus a single series from the 

 simple spheroidal to the most complicated types. 



As regards bathymetrical range, the Jurassic Thurammina 

 popillata is found in greatest number in the deposits with 

 true deep-sea character, much more rarely and in less typical 

 specimens in those formed at moderate depths. As the distri- 

 bution of the recent T.jpopiUata is world-wide*, its oldest 

 fossil representatives seem to be present in the deep-sea sedi- 

 ments all over Europe in countless modifications, many of 

 which have not been found in a recent state. On the other hand 

 the globular large varieties with small papillae and very finely 

 arenaceous tests of our existing seas are not known in a fossil 

 condition. 



The tests of all the Jurassic specimens of T. papillata are 

 very thin, composed of small grains of quartz-sand, neatly 

 fitted together, and united by a colourless, brownish, or yellow 

 cement. 



In describing briefly the various groups, I hope to add to 

 the knowledge of the Thurammince y as well as to that of the 

 Foraminifera in general, in connexion with the great variability 

 of certain forms and the wide geological range of species 

 characteristic of the deeper parts of the present sea. 



1. Test free, small (0*1 million.), more or less spheroidal. 

 Papillae disposed regularly or irregularly all over the surface. 

 Test finely arenaceous, generally colourless, or of a light 

 brownish colour. A single specimen from the Btmammatus- 

 beds of the Portuguese Jurassic formation showed a very 

 dark brown colour. These forms sometimes resemble Thuram- 

 mina albicans, Brady, with which they are found associated in 



the Upper Jurassic zones, especially in the sponge-beds of the 

 Argovian and Sequanian stage, all over the continent. 



Figs. 1-4 represent the more characteristic varieties, and 

 fig. 25 a larger specimen with numerous papillse. A typical 

 specimen from the Bimammatus-beds of Baden (Cant. Aargau) 

 is figured in N. Jahrb. f. Mill. 1883, Bd. i. tab. iv. fig. 10. 



2. Test free, compressed, generally symmetrical, large 



(0 # 5-l millim.). Papillae numerous, disposed all over the 



surface. Colour yellow. The finest specimens from the 



sponge-beds of the Lower Malm (zone of Ammonites trans- 



versarius) are almost transparent and of a characteristic yel- 

 lowish colour (fig. 21). 



* Brady, /. c. p. 27. 











