Reviews — Dr. G. J. Ilinde on Fossil Radiolaria. 31 



investments and their bizarre outgrowths. The clue, however, as 

 noted above, is aftbrded by the innermost organ. 



This is itself lost to the geologist, but its latticed capsule, and 

 the radial spines which partly term the transverse bars and beams 

 of the whole organism, may have remained, more or less imbedded 

 in limestones, shales, and sandstones, probabl3' altered into marbles, 

 schists, and qnartzites. Indeed, many fine-grained siliceous rocks 

 now appear to have resulted from Radiolarian ooze itself. 



In comparing the fossil and the recent specimens, the student has 

 to recollect that the general form is either globular, ellipsoidal, or like 

 vases, caps, umbrellas, discs, irregular stars, chambered cones, etc., 

 all perforate, fenestrate, or reticulate, with the meshes lengthening 

 out into spines on the surface or at the edges. The radial rod-like 

 spines, whether or not beginning in the middle of the nuclear lobe, 

 are often united by branching spicules at or near the surface of the 

 calymma, and similarly become involved in the outer lattice-shell. 



In the 8pumellaria the skeleton, if present, consists of either pure 

 silica or of a peculiar silicate (silicate of carbon ?) ; the rods are 

 solid, as in the Nassellaria, and do not begin in the centre. In the 

 Acantharia the rods begin in the centre, and consist of acanthin. In 

 the Nassellaria the skeleton is siliceous ; the rods are solid, usually 

 monaxial, and belong to the outer capsule (calymma). In the 

 Pha3odaria the skeleton consists of a silicate, and belongs to the outer 

 capsule. 



Radiolaria from strata of Tertiary age have been examined by 

 many observers. Some are figured bj^ Ehrenberg, who gave neatly 

 executed drawings, but did not otherwise advance our scientific 

 knowledge of these microzoa. In his " ]\likrogeologie," ISoi, some 

 Radiolaria appear (as ' Polycystina ') from Tertiary beds at iEgina, 

 Zante, and Caltanisetta, Sicily. These are noted, as to their 

 geological age, in the Ann. Mag. Nat. Hist., ser. iv, vol. ix (1872), 

 pp. 223, 225, and 228. 



IMessrs. Jukes-Browne & Harrison, treating of the siliceous rocks 

 of Barbados (Quart. Journ. Geol. Soc, vol. li, 1892, pp. 193-4), refer 

 to Haeckel's statement that many of the Barbadian Radiolaria are 

 not known in the modern oceanic ooze, and that about; 25 per cent, 

 of those fossil forms are present in the ooze. These results are taken 

 as determining a Pliocene age for the West-Indian siliceous strata 

 referred to. 



Cretaceous Radiolaria have been freely studied : for instance, by 

 Riist, 1888 ; Zittel, 1888 ; Pernet, 1891 ; Fritsch, 1893 ; Hill & Jukes- 

 Browne, 1895 ; and Cayeux, 1897. They have not, however, been 

 fully classified and strictly compared with other faunfe. 



Jurassic Radiolaria are known chiefly from Dr. Riisf's Memoir in 

 the " Pala^ontographica," vol. xxxi (1885). 



M. Lucien Cayeux^ has compiled a table of the geological 

 occurrence of Radiolaria of Mesozoic and earlier date, in which he 

 refers 



^ "Contribution a 1' etude micrograpliique des Terrains sedimentaires, etc." (tto, 

 Lille, 1887), p. 206. The Cretaceous Radiolaria of France and Belgium are dealt 

 nvith at pp. 185-206 and 450-452, pis. vii and viii. 



