342 Mr. E. H. L. Schwarz on Coccoliths. 



their occurrence in all the known strata, even the earliest. 

 W allien ' first noticed that they were joined into spherical 

 masses, which he called coccospheres * ; in his later papers 

 he considered these spheres as nothing else than embryonic 

 foraminifera covered with coccoliths as spicules, and figures a 

 Nodosaria and Textularia made up of such coccospheres. Sir 

 Wyville Thomson, according to Wallich, noticed that, if 

 threads be hung in sea-water overnight, they will be found 

 to be full of coccoliths in the morning ; so that these bodies 

 are really found on the surface of the ocean, and not only at 

 great depths, as those who do not believe in their organic 

 nature have maintained. 



I first came to notice coccoliths when systematically 

 washing the clays from the lias of the Dorset coast, where I 

 found them in about 60 per cent, of the zones treated. They 

 were most abundant, however, in a grey micaceous clay con- 

 taining Ammonites (Schlotheimia) angulatus, Schloth., and a 

 foraminifer, Nodosaria, which, according to Mr. F. Chapman, 

 resembles N. calomorpha, Reuss. The coccoliths in this clay 

 are peculiar in their transparency and for the great numbers 

 of the double cyatholith forms, which nowhere else have I 

 found in such abundance ; and the following details have 

 been obtained mostly from this material, though I have also 

 used the chalk of Taplow and the gault of Folkestone. 



The adult discoliths are minute oval bodies ^cro mcn 

 (Wallich) in their long diameter (figs. 2, 8, 9). In their 

 centre is a bright highly refractive body, the " Centralkorn " 

 of Hseckel, which is usually slightly, but frequently also 

 markedly, raised above the surface as a knob when seen from 

 the side ; but I have never seen it forming a projecting rod, 

 as Sollas f has figured from the Cambridge greensand. In 

 the flat area surrounding the central point, the <l Markfeld " 

 of Hseckel, there are two or four slightly raised points, similar 

 to the central one, but not nearly so much differentiated. 

 Round the " Markfeld " is the " mark-ring," which is a 

 refractive ring of calcite forming a thick rounded rim to the 

 little plate, and in the older examples is slightly beaded. 

 Hgeckel then notices that this, which I consider to be the 

 adult coccolith, surrounds itself with a granular ring (fig. 3), 

 and finally with another brightly illuminated outer ring (fig. 4). 

 This I take to be the first stage of the discolith (adult cocco- 



* Ann. & Mag. Nat. Hist. 1860, vi. p. 457 ; ibid. 1861, viii. p. 52 ; ibid. 

 1862, ix. p. 30 ; Royal Institute Proc. 1858, p. 299 ; Franklin Institute 

 Journal, xlii. 1861, p. 237 ; Quart. Journ. Micr. Sci. 1869, 1870, 1871, 

 1877, 1878. 



f Geol. Mag. 1876, pi. xxi. fig. 17. 



