7S EXPEDITION OF THE "ALBATROSS," IS'.W-IDOO. 



The same may probably be said of the Eadiolarians. The surface Radiolarians are 

 less numerous than the species living near the bottom, but the pelagic species occur 

 in such hosts as to outweigh at certain localities those living on the bottom. The 

 number of pelagic species of Radiolarians^ is far greater than that of the Globigerina?, 

 and there are no groups of the former living attached to the bottom, as in the case with 

 the arenaceous and porcellanous types of Foraminifera. On tlie other hand there must 

 be living and floating in close proximity to the bottom, far from continents and at depths 

 greater than 2000 fathoms, hosts of abyssal Eadiolarians, among which the Nasselaria 

 and the Phteodaria predominate. As a general rule the abyssal forms are characterized 

 by their smaller size and massive skeletons, while the surface types are distinguished 

 by their more delicate skeletons.'' The surface and pelagic Radiolarians probably do not 

 extend far be3'ond 200 fathoms in depth, and belong especially to the Spumellaria and 

 Acantharia, and, according to Haeckel, with but few Osculosa, and fewer Phseodaria than 

 Nassellaria. Unfortunately, no detailed account of the bathymetrical range of the 

 miuor groups of Radiolarians accompanies the report of Haeckel, ^ but he naturally 

 attaches the greatest significance to the dependence of their geographical distribution 

 on oceanic currents. 



The bottom deposit at the stations in the vicinity of the Marquesas are 

 characterized by an admixture of Globigerina ooze and volcanic particles. 

 In the channel separating the Marquesas from the northwestern Pau- 

 niotus, a distance of not more than 450 miles, the deeper parts, in from 2456 

 fathoms to 2700 fathoms, are marked by all the characteristics of the 

 deposits in the deeper parts of the eastern Pacific nortli of the Marquesas ; 

 the deposits passing from red clay associated with Radiolarians to red clay 

 mixed with Foraminifera, and in the lesser depths, 1208 fathoms to 1932 

 fathoms, we meet with deposits consisting of Globigerina ooze, and finally 

 coral sand in the vicinity of the Pauniotu Plateau. 



Again in the channel separating the Paumotus from the Society Islands 

 a deposit allied to red clay, compo.sed in part of Globigerina?, was found 

 in the deeper parts at a depth of somewhnt over 2200 fathoms; the Glo- 

 bigerinoe becoming mixed with large proportions of volcanic mud as we 

 approached the Society Islands. 



' ILieokel pniimcrates more than 4300 ?pe<:ies, and remarks that prolialily twice that number 

 could be (listins;uislied from a more detailed ex.imination of the " Clinllen^er " material. Report 

 on tlie I'>.-i<iiolaria collected by II. M. S. "Challenger," 1887. Zoology; Vol. XVIII., First 

 Part, |). ii. 



^ Haeckel, 1. c , p. clli. 



* Haeckel, 1. c., p. cxlvi. 



