DR. SCHULTZE, ON THE RHIZOPODA. 149 



third including a small number of species hitherto over- 

 looked, and united by Dr. Schultze in the genus Acervulina. 

 In Dr. Schultze's arrangement these three divisions constitute 

 as many groups, under the names of Rhabdoidea, Helicoidea, 

 and SoRoiDEA. 



The Monothalamia he subdivides into three families. The 

 first embracing all the forms having a sacciform, solid, cal- 

 careous, or membranous test, with a single large opening. 

 The second is constituted of the single genus Orbulina, D'Orb. 

 yMiliolu, Ehr.), and is distinguished from the preceding by 

 the globose, calcareous test, having no large opening, and per- 

 forated all round hy fine pores. The third family, lastly, in- 

 cludes the genus Cornuspira (Schultze), having a monothala- 

 mous, calcareous shell, convoluted like that of a Planorbis, 

 and furnished with a large opening. 



The following tabular arrangement of the Rhizopoda is given 

 by Dr. Schultze, with which we must conclude this notice 

 of his most valuable work. 



RHIZOPODA. 



A. NUDA. 

 Gen, Amceba (Noctiluca?) 



B. TESTACEA. 



I. Monothalamia, 

 Test one-chambered ; animal luidivided. 



1. Fam. Lagynida. — A sacciform, calcareous, or membranous, nou-porous 



test, with a large opening. 

 Gen, Arcella, Difflugia, Trineraa, Euglypha, Gromia, Lagynis, 

 Ovulina, Fissurina, Squamulina, &c. 



2. Fam. Okbulinida. — A globose, calcareous test, without a large open- 



ing, and finely porous throughout. 

 Gen. Orbulina. 



3. Fam. Cornuspirida. — A calcareous test, convoluted like the shell of a 



Planorbis, with a large opening. 

 Gan. Cornuspira. 



II. POLTTHALAMIA. 



Shell polythalamous ; the animal constituted of segments, connected by 

 slender processes. 



1. Group Helicoidea. 

 The chambers disposed in a spiral. 



4. Fam. Miliolida. — Each chamber occupies a half-spiral ; the spires 



developed either in one plane or in various planes. 

 The shell has only one large opening at the 

 extremity of the last spiral. No poros. 

 Gen, Uniloculina, Biloculina, Miliola, Spiroloculina, Articu- 

 lina, Sphaeroidina, Adelosina, Fabularia. 



