March n, 1880] 



NATURE 



449 



the Brockenhurst series, not more than one-fifth occur in 

 the Barton clay (Upper Eocene) below. The Hempstead 

 marine fauna has still fewer species in common with the 

 Eocene. 



The late Sir Charles Lyell proposed to divide the fluvio- 

 marine series into two portions, and to group one with the 

 Eocene and the other with the Miocene. But the incon- 

 venience of breaking up this homogeneous series of beds 

 into two portions must be apparent to every one. 



Under these circumstances it is felt by geologists that 

 the fluvio-marine strata of the Hampshire basin must be 

 referred to a division of the Tertiaries distinct alike from 

 the Eocene and the Miocene, and this was admitted by 

 almost every one who took part in the discussion last 

 Wednesday, including Prof. Prestwich and Dr. Duncan. 



In the year 1854, Prof. Beyrich, of Berlin, showed that 

 under the great masses of gravels and drift that cover 

 such large tracts in North Germiny,and immediately over- 

 lying the great Brown-coal formation of the country, there 

 exist marine beds which contain a fauna distinct alike 

 from the fauna of the Miocene and from that of the 

 Eocene ; and strata containing the same fauna have 

 since been discovered in the Netherlands, Switzerland, 

 and other parts of Europe. For the division of the ter- 

 tiary series which contains this fauna, Beyrich proposed 

 the name of the Oligocene. Whether or not its author 

 was happy in the choice of this name, no one can doubt 

 that he has sufficiently demonstrated the distinct charac- 

 ter of the great system of beds to which he applies it. 



In 1867 von Koenen and Duncan, from a study of the 

 molluscan 3nd coral fauna of the Brockenhurst beds, 

 respectively, proved that the fluvio-marine strata of the 

 Hampshire basin represents the North German Oligocene; 

 and the justice of this correlation is placed beyond doubt 

 in the memoir by Prof. Judd which has just been re d. 

 He shows that the Headon group and the Brockenhurst 

 series represent the lower Oligocene, while the Bembridge 

 group and the Hempstead series are the equivalents of 

 the lower part of the middle Oligocene, the upper Oligo- 

 cene not being represented in this country. 



That the Oligocene is a very important division of the 

 geological series is shown by the fact that in Eastern 

 Europe (Hungary and Transylvania) strata of this age 

 attain a thickness of between 2,000 and 3,000 feet, and 

 contain valuable beds of coal, while in the neighbourhood 

 of the Alps they are from 10,000 to 12,000 feet thick. It 

 is interesting to find that the lower portion at least of 

 this great formation is represented in our own country, 

 and by strata of such thickness and importance. 



A NEW CLASS OF RHIZOPODA 



A T a meeting of the Natural History Society of Jena 

 •**■ the following note was read by Prof. Ernst Haeckel : 

 " Upon the Ph.eodaria, a new Group of Marine Siliceous 

 Rhizopods." 



The Phaeodar a are a group of large marine Rhizopods, 

 rich in specific forms and remarkable in many respects, 

 which have hitherto been included in the typical Radiolaria 

 (Sphaeridea, Discidea, Cyrtidea, Cricoidea), from which 

 they differ as widely as do the Acanthometrina. Till 

 lately very few forms of the Phaeodaria were known ; 

 these were first observed by me at Messina in 1859, and 

 described in my monograph of the Radiolaria in 1S62, as 

 representatives of three different families — 



1. Aulacanthidae (genus Aulacanthd). 



2. Aulosphaeridae (genus Aulosphara). 



3. Ccelodendridae (genus Calodendruni). 



Besides these, I had described two other forms belong- 

 ing to this group, namely, Thalassoplancla, which I 

 placed among the Thalassosphaeridae, and Dictyocha, 

 which I placed among the Acanfhodesmidae. 



Quite a new light has been thrown upon these interest- 



ing Rhizopods by the Challenger expedition, which dis- 

 covered so many forms of the typical Radiolaria in the 

 depths of the Pacific Ocean, that I have been able to 

 define more than 2,000 new species. Besides these, the 

 explorations of the Challenger have brought to light a 

 number of deep-sea Phaeodaria hitherto entirely unknown. 

 The number of species of this group in the surface pre- 

 parations in the Challenger collection which have been 

 examined by me is not so considerable. 



John Murray gave, in 1876, a short account of some of 

 the most peculiar forms of these new deep-sea Phaeodaria, 

 under the name of Challengeridoe (Proceedings of the 

 Royal Society, 1876, vol. xxiv. pp. 471, 535, 536, PI. 24, 

 Figs. 1-6). He draws particular attention, on the one 

 hand, to the extremely delicate and finely-fenestrated 

 structure of the large siliceous shells, and on the other 

 hand to the constant appearance of masses of black- 

 brown pigment which are scattered through the sarcode, 

 outside the central capsule. 



In the new arrangement of the Radiolaria given by me 

 in 187S, in my article on the "Protista" (Kosmos, 

 vol. iii.), I placed the hollow-spined siliceous Phaeodaria 

 already mentioned in a special order of Radiolaria, under 

 the name of " Pansolenia : ' : "The skeleton consists of 

 single hollow tubes, loosely scattered, or connected in 

 radial or concentric order" (" Protistenreich," p. 102). 



This group was described in 1879 by Richard Hertwig, 

 in his work on "The Organisation of the Radiolaria," 

 as a special order of the class under the name of " Tri- 

 pyleae," with the following characters: — "Radiolaria 

 Monozoa, with single nuclei ; capsule-membrane double, 

 with one principal and two lateral openings ; skeleton 

 siliceous, formed of tubes" (I.e., p. 133, p. 87). 



Neither the name "Tripylese," given by Hertwig, nor 

 my name " Pansolenia " is applicable to all the Rhizopods 

 which I have now placed in the group Phaeodaria, as only 

 a portion of these have the three openings in the double 

 membrane of the central capsule, which ought to charac- 

 terise the " Tripylea" and in a portion of them only the 

 siliceous skeleton is formed of " hollow tubes " ("Panso- 

 len/tr 1 '). On the other hand, as Murray first snowed, a 

 striking character of all these Rhizopods is the constant 

 presence of large dark-brown pigmented granules, scattered 

 irregularly round the central-capsule, and covering the 

 greater part of its outer surface. In brevity I call this 

 extra-capsular mass of dark pigment the Phaeodium (<pai6s 

 or <j>moit>t]s = dark brown, dusky). The Pbaeodella, or 

 large brown granules of the Phaeodium are not, as Murray 

 supposed (I.e., p. 536) true pigment cells, as a true cell 

 nucleus cannot be observed in them'; and the nature of 

 the peculiar pigment of these pseudo-cells is not precisely 

 known ; but the quantity and constancy with which the 

 Phaeodium appears in all Phaeodaria, while it is wanting 

 in all the typical Radiolaria, gives the Phaeodaria a high 

 degree of systematic importance. It seems to me at 

 present that the constant presence of the Phaeodium and 

 the peculiarly constructed membrane of the central- 

 capsule are the only systematically reliable characters 

 which separate all Phaeodaria from all other Radiolaria. 



The size of the Phaeodaria is usually very striking in 

 comparison with that of the other Radiolaria, which they 

 greatly surpass in diameter. The greater number of the 

 Phaeodaria are visible to the naked eye, and many are 

 from .V 1 mm. or more in diameter. The conspicuous 

 central capsule is usually round or spheroidal ; it is, how- 

 ever, often egg-shaped or somewhat oval. In many cases 

 it is monaxial, in others dipleuric. Its membrane is very 

 firm and always double, the outer layer very thick, the 

 inner thin. The opening through which the pseudopodia 

 appear has the very peculiar structure accurately described 

 by R. Hertwig (1878, I.e.). Many Phaeodaria have only 

 one such opening (Monopylecc), others have two at the 

 opposite poles of the central capsule (Amphipylece) ; 

 many, perhaps the greater number, have three, one larger 



