242 GENEKAL HISTOEY OF THE INFUSORIA. 



anterior wall of the first chamber on the under side looking towards 

 the penultimate spiral ; the communicating openings of the several 

 chambers have a similar position. 



Gen. Nonionina, Hauerina, Orbignyna, Fusulina, Nummulina, Assilina, 

 Siderolina, Amphistegina. Operculina and Heterostegina should pro- 

 bably be formed into a special subfamily of Nonionida. 

 Subfam. 3. Peneroplida. — Shells usually thin, always brown, and transparent with or 

 without fine pores ; the chambers very narrow, either imbricate or not. 

 Numerous openings, scattered over the whole of the anterior wall of 

 the last chamber ; or, instead of these, a lai'ge opening produced by 

 the coalescence of ntmierous smaller ones. 



Gen. Peneroplis, Dendritina, Vertebralina, Coscinospira, Spii'olina, Lituola. 

 Appended genus, Orbiculina. 

 Subfam. 4. Polystomellida. — Shell tolerably thick, colourless, transparent, finely por- 

 ous ; chambers imbricated ; the anterior wall of the last chamber 

 has, besides the fine pores, either no larger opening at all, or a few 

 very small irregular scattered fissures, on the contrary side to the 

 penultimate whorl. The same applies to the septa. On the surface 

 of all the chambers, rows of fissure-like, often perforating, depressions 

 are placed at right angles to the direction of the septum. 



Gen. Polystomella. 



Fam. 7. Alveolinida. — Globose, ovoid, or barley-shaped shells, composed of spiral tubes, 

 each resembling a cornuspira, and fm*nished with a special opening 

 at the end of the turn or spiral. The tubes all commimicate by con- 

 necting openings, and, besides this, are all subdivided by incomplete 

 dissepiments (partitions), in the same manner as species of Nonionina. 

 The situation of these septa, which are but few in number, and of the 

 coimecting openings, is indicated by lines, which traverse the shell in 

 the direction of meridional lines. 

 Gen. Alveolina. 



Fam. 8, Soritida. — Discoid, multicellular shells, exhibiting an indication of a helicoid 

 spiral only in the centre ; elsewhere cycloid, that is, growing uniformly 

 at the whole border of the disk. The brown, transparent, finely porous 

 shell is formed of minute chambers, connected together in the direc- 

 tion of straight or curved radii, and each presenting a large opening 

 at the border of the disk. 

 Gen. Sorites, Amphisorus, Orbitulites. Appended genus, Cyclolina (cham- 

 bers perfectly annular, with numerous openings on the border of the 

 disk). 



2. Group Ehabdoidea. 

 The chambers piled one on another, in a straight or slightly curved line, in a single row. 



Fam, 9. Nodosarida. — Eod-shaped shells, whose chambers are superimposed one upon 

 another in a row, and communicate with each other by a large 

 opening; a similar opening in the last chamber (except in the 

 genus ConuUna, which has numerous openings instead of the single 

 one). The shell visually thick, probably always perforated by fine 

 pore-canals. 

 Gen. Glandulina, Nodosaria, Orthocerina, Dentalina, Frondicularia, Lin- 

 gulina, Rimulina, Vaginulina, Webbina, Conulina. 



3. Group SOROIDEA. 



Chambers grouped in irregvdar masses. 



Fam. 10. AcERVULiNiDA. — Chambers usually globose, disposed very irregularly, and of 

 pretty uniform dimensions ; shell finely perforate, with a few larger 

 openings at. indeterminate places. 

 Gen. Acervulina. 



The preceding account of the Ehizopoda we believe to be ample to lead the 

 student forward in the study of that peculiar class of animals. Yet, with re- 

 spect to the division Foraminifera it may be considered less complete : for, 

 from the close attention given of late to those beings, every monthly and 

 quarterly periodical of natural science teems with fresh facts and opinions 

 concerning them ; and, above all, we have had placed in our hands, since the 

 foregoing history was written, the very elaborate and critical researches of 



