REPORT ON THE RADIOLARIA. clxxiii 



248. Radiolarian Quartzes. Under the name Radiolarian or Polycystine quartzes 

 are included those hard, siliceous rocks, which consist for the most part of the closely 

 compacted shells of SPUMELLARIA and NASSELLARIA. To these " cryptocrystalline 

 quartzes," or better, quartzites, belong more especially the pure Eadiolarian formations of 

 the Jura, which have been described as flint, chert, jasper, as well as other cryptocrys- 

 talline quartzites. Most of the rocks of this nature hitherto examined are from Germany 

 (Hanover, South Bavaria), Hungary, Tyrol, and Switzerland ; others are known from 

 Italy (Tuscany). They occur both in the upper and middle, but especially in the lower 

 Jurassic formation (also in the lower layers of the Alpine Lias). A small part of them 

 has been examined in their primary situation (the red jaspers of Allgau and Tyrol), the 

 greater part, however, only as loose rolled stones in secondary situations (thus in Switzer- 

 land in the breccia of the Rigi, in the conglomerate of the Uetli-Berg, and in many 

 boulders of the Rhine, the Limmat, the Reuss, and the Aar). The greatest abundance, 

 however, of Jurassic Radiolaria has been yielded by the silicified coprolites from the Lias 

 of Hanover. These " Radiolarian coprolites " are roundish or cylindrical bodies, which 

 may attain the size of a goose-egg ; they probably originated from Fish or Cephalopods, 

 which had fed upon Crustacea, Pteropoda, and similar pelagic organisms, whose stomachs 

 were already full of Radiolarian skeletons. Next to the coprolites the richest is the red 

 jasper, whose colour varies from bright to dark red ; it constitutes a true " silicified deep- 

 sea Radiolarian ooze." The " Aptychus beds " also of South Bavaria and Tyrol are very 

 rich, and have furnished about one-third of all the Radiolaria known from the Jura ; most 

 of the species too are very well preserved (compare 243). 



Regarding the remarkable composition and manifold varieties of the Jurassic Eadiolarian quartz, 

 the very full treatise of Dr. Eiist may be consulted (L. N. 51). The very interesting Eadiolarian 

 coprolites, which that author has discovered in the lower and middle Jura of Hanover, occur in 

 astonishing numbers in the iron mines at the village of Gross-Ilsede, four and a half miles south of 

 the town of Peine. They constitute from 2 to 5 per cent, by weight of the Liassic iron ore; of 

 this latter, in the year 1883 alone, not less than two hundred and eighty million kilograms were 

 excavated. It is very probable that the careful microscopic examination of thin sections of 

 coprolites, as well as of flints, chert, jasper, and other quartzites, would yield a rich harvest of 

 fossil Eadiolaria in other formations also. In Italy Dante Pantanelli has discovered interesting 

 Polycystine jaspers in Tuscany (L. N. 36, 45) ; these also appear to occur in the Jura (compare 

 243, and L. K 51, pp. 3-10). 



249. Fossil Groins. The preservation of Radiolaria in the fossil state is, of course, 

 primarily dependent on the composition of their skeleton. Hence the ACANTHARIA, 

 whose acanthin skeleton although firm is readily soluble, are never found fossil. The 

 same is true of the skeletons of the PH^EODARIA, which consist of a silicate of carbon ; 

 here, however, a single exception is found in the Dictyochida, a subfamily of the 

 Cannorrhapida, the isolated parts of whose skeletons appear to consist of pure silica, and 



