en 



THE VOYAGE OF H.M.S. CHALLENGER. 



1881). These different views are regulated, on the one hand, by the known extent of the 

 group and by the amount of our acquaintance with it, and on the other, by comparison 

 with related groups and by reference to their conventional disposition. When, therefore, 

 the whole class, Eadiolaria, is here divided into two subclasses, four legions, eight orders, 

 eighty-five families, &c., these artificial categories are drawn up only in the conviction 

 that by this means the easiest survey and most thorough insight into the system as a whole 

 may be attained ; this latter will indeed approach as far as possible the ideal of a natural 

 system, but must on numerous practical grounds always remain more or less artificial. 

 Since it is to be expected that with the progress of our systematic knowledge the rank of 

 the various categories will rise, it is possible that in the future the arrangement of the 

 group may be somewhat as follows : — Phylum, EADIOLARIA ; Four Classes, Spumel- 

 LARiA, Nassellaria, Acantharia, Ph^odaria ; Eight Legions (Nos. I.-VIII. in the 

 following Table); Twenty Orders (Nos. 1-20 in the Table), &c. 



Four Legions. 



I. Legion (or Subclass) 

 Spumellaria 

 (Peripylea). 



[^PoTulosa peripylea.'] 



II. Legion (or Subclass) 

 Acantharia 

 (Actipylea). 



\Porulosa actipylea.] 



Eight Sublegions. 



I. CoUodaria 



{Spumellaria palliata) 



II. Sphserellaria 

 {Spumellaria loricata) 



III. Acanthometra 



{Acantharia palliata) 



\ 1. 



IV. Acanthophracta 



{Acantharia loricata) 



5. 



Twenty Orders. 

 Colloidea, . 



Beloidea, 



Spliaeroidea, 



Prunoidea, 



Discoidea, 



6. Larcoidea, 



7. Actinelida, 



8. A c a n t h o u i d a, 



9. Sphserophracta, 

 P r u n p h r a c t a, . 



Typical Families. 



la. Thalassicollida. 



1 b. Collozoida. 



2a. Thalassosphaerida. 



2b. Sphaerozoida. 



j 3a. Ethmosphajrida. 



I 3i. Collosphferida. 



( 4a. EUipsida. 



\ ib. Zygartida. 



10. 



5a. Phacodiscida. 

 5b. Porodiscida. 



{ 



j Ga. Larnacida. 

 I Qb. Pylonida. 



7a. Astrolophida. 

 7b. Litholophida. 

 7c. Cliiastolida. 



8a. Astrolonchida. 

 8b. Quadrilonchida. 

 8('. Amphilonchida. 



9a. Sphserocapsida. 

 9b. Dorataspida. 

 9c. Phractopeltida. 



10a. Belonaspida. 

 10/'. Hexalaspida. 

 lOf. Diploconida. 



