On the Stiiidure of Coccosphercs and the Origin of Coccoliths. 305 



„ 7<?. The same still further developed and after the incorporation of some 

 outer cseca. 



„ If. A section across the complete calicle with its twelve well-developed septa. 

 *lg. The calicle as seen from the surface of the corallum. 

 Fig. Sa-c. Seliopora somaliens^is, n.sp. Turonian. XJradu, Somaliland. B.M., 

 K4150. 



„ 8a. Part of a horizontal section with two calicles. x 15 diam. 



„ 8b. Part of a horizontal section showing circular and angular "cseca," the 



latter being in the upper portion, which is filled with quartz-grains. 



X 10 diam. 



„ 8c. Part of a horizontal section, showing three calicles, with and without 

 septal ridges, x 15 diam. 



On the Structure of Coccospheres and the Origin of Coccoliths." 

 By Hexry H. Dixon, Sc.D., Assistant to the Professor of 

 Botany, Trinity College, Dublin. Communicated by J. JoLY, 

 r.E.S., Professor of Geology, Trinity College, Dublin. Eeceived 

 February 3,— Eead February 22, 1900. 



[Plate 3]. 



At the beginning of September last year, I visited Valencia, Co. 

 Kerry. It occurred to me there that coccospheres might possibly be 

 drifted in on the warm current of the Gulf Stream, which impinges 

 on the south-west coast of Ireland, and as they float in would become 

 entangled in the sea-weeds on the coast. With this idea, I gathered 

 some of the finer marine algae, such as species of Cladophora, Polysi- 

 phonia, and Plocamium, &c., from the rock pools in Valencia Harbour. 

 Taking care to wash as little of the silt or sediment as possible from 

 them, I fixed the mass in dilute formalin. 



This method proved to be a most satisfactory way of collecting 

 coccospheres and coccoliths. In the first sample of sea-weeds thus 

 gathered at a venture, I obtained several hundreds of coccospheres, 

 and of course innumerable coccoliths. In practice, the most convenient 

 way of gathering coccospheres in abundance was found to be to 

 collect the sea-weed, and there and then to wash the sediment from it 

 in sea-water and formalin, or in alcohol, or in sea-water and osmic 

 acid. The sediment which settles down in the fixing fluid will after- 

 wards be found to contain large niunbers of coccospheres. In pre- 

 parations made from material collected in this manner, and mounted 

 under a cover-glass 22 mm. x 22 mm., I have counted as many as 

 fourteen coccospheres. Of course there are many other organisms 

 present in addition to the coccospheres, e.g., various Crustacea, mites, 

 worms, molluscs, foraminifera, infusoria, diatoms, peridinese, &c. 



I am indebted for most of the material from which the following 



