Revieivs — Dr. Riist on Fossil Radiolaria. 327 



sfrata. The Eadiolaria mainly occur in jaspers, chert or hornstone, 

 siliceous shales and slates, and siliceo-calcareous beds ; but in the 

 numerous Palaeozoic limestones examined by the author, they are 

 extremely rare and in bad preservation. In some of the siliceous 

 rocks they are so abundant as evidently to form the main portions 

 of the substance of the rock ; as a rule they are, however, too poorly 

 preserved to permit of specific determination ; but here and there 

 specimens are met vpith, usually in the form of hard nodular concre- 

 tions containing phosphatic, carbonaceous and manganese ingredients, 

 in which the structural details of the Radiolaria are wonderfully 

 shown, not infrequently owing to their being stained by these 

 accessory materials. Strange to say, these Palaeozoic Radiolai'ia are 

 in better condition than any yet known from Mesozoic rocks ; and 

 they are generally larger and possess stronger and more complicated 

 tests than the Mesozoic species, thus more nearly resembling Tertiary 

 and living forms. In the radiolarian -bearing rocks there are, occa- 

 sionally, sponge-spicules, and in some of Silurian age, fragments of 

 graptolites, but calcareous fossils are absent. 



The Triassic Radiolaria were principally obtained in beds of 

 chert of Middle and Lower Muschelkalk age, in the Tyrol, and at 

 Felso Eors in Hungary. In the Paleeozoic rocks the greatest 

 development of Radiolaria is met with on the lowest horizon of 

 the Carboniferous limestone, beginning at the Culm and reaching 

 downwards to the Upper Devonian. In the Harz, Hessen and 

 Waldeck, they are present in dark carbonaceous siliceous shales, 

 jaspers and chert, they also have been met with in the Ural and 

 possibly also in Sicily, in rocks of the same horizon. From these 

 v^arious localities 155 species have been described. In the Upper 

 Devonian rocks of the Hartz the Radiolaria occur in siliceous shales 

 containing manganese, but without carbonaceous material ; whilst in 

 the Lower Devonian of the Ural they are present in red jasper, and 

 on the same horizon in Hessen in siliceous shale, which the author 

 considers a true radiolarian mud. Altogether from Devonian strata 

 64 species have been recognized. 



In rooks of Ordovician or Lower Silurian age Radiolaria occur 

 in siliceous shales at Langenstriegis, in Saxony ; Bohemia ; Scotland ; 

 and more especially at Cabrieres in Languedoc, where they are 

 excellently preserved in phosphatic concretions loosely imbedded in 

 the shales. No compai'ison is made of the forms in the Scotch chert 

 with those from other localities, and no mention whatever of those 

 described in a paper published nearly two years since. In all 26 

 species are described by the author from Lower Silurian beds ; with 

 the exception of three forms, they have been derived from the 

 Cambrieres concretions. At a still lower horizon, in the Cambrian 

 rocks of Sonneberg, in Thuringia, Radiolaria are present, but their 

 specific characters cannot be distinguished. 



Out of 109 genera in which these Paleeozoic and Triassic forms 

 have been ranged, but two only are new. The 247 Paleozoic 

 species fall under the following orders in Haeckel's classification of 

 the group : Spheroidea, 81 sp. ; Prunoidea, 48 sp.; Discoidea, 52 sp. ; 



