REPORT ON THE RADIOLARIA. 1,339 



embedded iu a punctulate cenient-substauce), with hollow radial spines and with a corona 

 of simple solid teeth around the mouth ; (5) Tuscarorida (PI. 100), shell ovate or 

 subspherical, with smooth sui'face, of the same peculiar porcellanous structure as the 

 Circoporida, but with hollow, very long, tubular teeth around the mouth. 



The Phgeoconchia are the peculiar and most interesting " Ph^odaria bivalva," 

 diflering from all other Ph.^odaria, and from all known Eadiolaria in general, in the 

 possession of a bivalved lattice-shell, composed of a dorsal and a ventral valve. They 

 maybe divided into three families: (1) Concharida (PI. 123-125), shell with two 

 thick and firm, regularly latticed valves, which bear no hollow tubes and no cupola or 

 galea on their apex or sagittal pole; (2) Coelodendrida (PI. 121), shell with two 

 thin and fragile, scarcely latticed valves, which bear a conical cupola or a helmet-shaped 

 galea on their apex, and hollow branched tubes arising from it (without rhinocanna and 

 frenula); (3) Coelographida (PI. 122, 126-128), shell with two thin and fragile, 

 scarcely latticed valves, similar to those of the Ca3lodendrida, but differing from them 

 in the development of a peculiar rhinocanna or nasal tube upon each valve ; this tube 

 is connected by an odd or paired frenulum with the apex of the galea, and both 

 together contain the phgeodium. 



The phylogeuetic affinity of the fifteen families enumerated, and the morphological 

 relationship based upon it, form a very difficult problem. The whole legion of Ph^eodaria 

 is proljably monophyletic, in as much as all the families may be derived from a single 

 ancestral group, the skeletonless Phseodinida {PhcBodina and PhcBOColla) ; but at the 

 same time polyphyletic, in as much as probably many families have been derived, indepen- 

 dently one from another, from different branches of Phseodinida ; or in other words, 

 the characteristic malacoma of the Ph^eodaria (the cannopylean central capsule and the 

 ealymma with the phseodium) may be a mouo^ihyletic product, inherited from a single 

 ancestral form ; the manifold skeleton, however, is certainly a polyphyletic product, 

 originatino; from different skeletonless Phseodinida. 



Among the independent families of Ph/EOBARia, derived directly from skeletonless 

 Phseodinida by production of a peculiar skeleton, may be the following : Cannorrhaphida 

 (PI. 101, probably polyphyletic) Aulacanthida (PI. 102-105), Castanellida (PI. 113), 

 Challengerida (PI. 99), Concharida (PL 123-125), Circoporida (PL 114-117) and 

 Tuscarorida (PL 100). The four families of Phseosphseria (the Orospha^rida, 

 Sagosphserida, Aulosphserida and Cannosj)h8erida (PL 106-112), may be derived 

 perhaps from the Castanellida; and the Medusettida (PL 118-120), have been 

 perhaps derived from the Challengerida. The complicated affinities of these groups are 

 however difficult to explain. The Coelodendrida (PL 121) are probably derived from 

 the Concharida, and the Coelographida (PL 126-128) from the Coelodendrida. 



The geometrical fundamental form of the shell is in the majority of Ph^odaria 

 monaxonial, corresponding to the main axis of the enclosed central capsule ; the 



