552 SYSTEilATIC HISTOEY OF THE INFrSORIA. 



Changeable processes f Lorica spherical or tun -like Difflugia, 



radiant, generally -1 Lorica a flat spiral Spirilliua. 



numerous [ Lorica discoid or shield-shaped Aj-cella. 



Changeable processes broad and unbranched Cyphidium. 



The genus SpirlUina is a veiy exceptional form ; it has a spii^ally-coiled 

 shell, apparently porous throughout, Kke one of the Foraminifera, and like 

 them, too, a marine habitat. Its only affinity with the Ai'cellina, according 

 to Ehrenberg's account, is the silicious nature of the shell ; but even were 

 this established, it would not exclude it from the Foraminifera, among which 

 silicious testae are kno^vn. Of Ci/phidium little information exists ; and 

 Ehrenberg's account is by no means satisfactory. The same may be said of 

 the figures he gives of it. 



Dujardin divides the '* Ehizopodes," excluding the Amoebaea, into two sec- 

 tions, according to the form of the variable expansions. The first section cor- 

 responds to the family Arcellina of Ehrenberg, and comprehends those species 

 provided with short thick expansions, rounded at the extremity. Such are 

 the Diffiugice, 'possessing a flexible membranous lorica, without visible tex- 

 ture, mostly of globular form, from the aperture of which the expansions 

 radiate : such, too, are the Arcellce, having a discoid lorica, flattened on the 

 side along which they move (the plane of reptation), where is a central 

 round opening, from which the expansions proceed, the latter lying thus be- 

 tween the shell and the siu-face along which it glides ; the lorica, moreover, 

 is brittle, and often reticulated, or areolated. The second section, much 

 larger, comprises beings of every variety of form, and having very numerous 

 fllilbrm expansions, ending by very fine extremities. Of these varieties he 

 makes three tribes ; the first distinguished from the Difflugice only by the 

 slender character of the expansions, except that in one genus, Trinema, the 

 opening is lateral ; the second, represented by the genus Euglypha, having a 

 lorica beset with tubercles, or areolae, disposed spii-ally ; and the thii^d by the 

 genus Gromia, having a spherical membranous shell, and very long and 

 branching expansions. 



The remainder of the " Ehizopodes," as described by Dujardin, are com- 

 prehended in the Polythalamia by other authors. Of these he constitutes two 

 tribes, — one represented by the single genus Miliola, which, hke Gromia and 

 the examples of the first tribe, has but a single large opening in its 

 lorica for the escape of the expansions ; the other by several genera, all 

 of which give off numerous filiform expansions from many distinct pores 

 (foramina) of their shells, and hence called Foraminifera. 



Siebold included the first and second divisions of Dujar din's class Rhizo- 

 poda in his group of Arcellina. 



M. Schultze framed the division of the Monathalamia from the structure 

 of the shells ; but he admitted amongst them the genus Orhulina, which 

 possesses the very exceptional character of having numerous pores to its 

 shell, instead of a single opening. The three families instituted were: — 

 1. Lagynida; 2. Orbulinida; 3. Cornuspiiida (see p. 241). The first-named 

 family corresponds most nearly to Ehrenberg's Arcellina, although it con- 

 tains several genera usually described in histories of the Foraminifera, and 

 omitted by the Berlin natui'alist. The following are enumerated : — Arcella, 

 Difflugia, Cypliidium, Trinema^ Eughjpha, Gromia, Lagijnis, Ovulina (d'Or- 

 bigny), Fissurina (Eeuss), Squamulina, and the doubtful genera of Schluni- 

 berger — Lecquereusia, Cyphoderia, Pseudodijffiugia, and Sp)henoderia. The 

 genera Lagynis and Squamidina are two new ones formed by Schultze him- 

 self. It will make this history more complete to introduce these new genera 



