1522 THE VOYAGE OF H.M.S. CHALLENGER. 



constant in all members of the group. But this is by no means the case. The two 

 accessory openings are completely absent in several families, whilst in others their 

 number is increased. A constant and very striking character, however, of all PH^EODARIA, 

 is the peculiar structure of their tubular main-opening, which I call astropyle, with its 

 radiate operculum and cannular proboscis. On account of this important and startling 

 characteristic I proposed in 1881 to call this group CANNOPYLEA. The two names 

 PHJEODARIA and CANNOPYLEA both express a very striking and quite constant character 

 of these curious Radiolaria, whilst the two names PANSOLENIA and TRIPYLEA are applicable 

 only to a part of the whole legion. 



The history of our knowledge of the PELEODARIA is short, but very remarkable. 

 Although hundreds of species, many of them cosmopolitan, are distributed over all 

 oceans and all zones, although their size is in general much greater than that of the other 

 Radiolaria (usually 1 to 2 mm., often even 5 to 10 mm. or more), and although their form 

 and structure are usually striking, nevertheless the PH.EODARIA remained completely 

 unknown up to the year 1859. During that year I observed the first forms living in the 

 Gulf of Messina, and described and figured in 1862 in my Monograph five genera and 

 seven species, viz., (1) Aulacantha scolymantha (p. 263), (2) Tlialassoplancta cavispicula 

 (p. 261, now Cannobelos cavispicula), (3) Aulosphcera trigonopa, and Aulosphcera 

 elegantissima (p. 359), (4) Spongodictyum trigonizon (p. 459, now Sagoplegma trigonizon), 

 and (5) Ccelodendrum ramosissimum, and Ccclodendrum gracillimum (p. 361). I 

 recognised the structure of the three genera enumerated as 1, 3, and 5, as so remarkable 

 and so different from that of the other Radiolaria, that I founded three peculiar 

 families for them, the Aulacanthida, Aulosphaerida, and Ccelodendrida. 



The first note on the numerous remarkable PH^ODARIA discovered by the Challenger, 

 and mainly on the large-sized inhabitants of the deep-sea, was published in 1876 by Dr. 

 John Murray, in his Preliminary Reports on Work done on Board the Challenger (Proc. 

 Roy. Soc., vol. xxiv., read March 16, 1876). He pointed out (loc. cit., p. 535), that the 

 tow-nets, sent down to a great depth (according to a new plan, adopted in April 1875) 

 brought up on every occasion a great many new and peculiar Rhizopods, which had 

 never been observed in the nets used near the surface. " The shells of all have an 

 exceedingly beautiful tracery, a fenestrated appearance often, which a closer examination 

 shows to be caused by pit-like depressions. Some have only one, others have several 

 openings, through which the sarcode flows. The sarcode of all these deep-sea Rhizopods 

 has many large black-brown pigment-cells. At times they come up with a good deal of 

 the sarcode outside of the shell ; and two specimens have been seen to throw out 

 elongated pseudopodia" (loc. cit., p. 536). Dr. John Murray distinguished at that time 

 not less than fifty species of these interesting deep-sea Rhizopods and called them 

 provisionally Challengerida ; a term which we retain here for the largest and most 

 characteristic family. He gave at the same time, in an accompanying plate (xxiv.), six 



